














o> ^K 
























ELEMENTARY BOTANY 



GEORGE FRANCIS ATKINSON, Ph.B. 

Professor of Botany in Cornell University 




NEW YORK 

HENRY HOLT AND COMPANY 

1898 



Copyright, 1898, 

BY 

HENRY HOLT & CO. 




TWO COPIES RECEIVED* 






81965 OCT 21 181 







ROBERT ORUMMOND, PRINTER, NEW YORK. 



loss. 



/; 



PREFACE. 

Untij recent years the prevalent method of teaching botany 
in the secondary schools, and in the first courses in many col- 
leges, has been based on the . " analysis " of flowers. The 
method had its impetus in the study of systematic botany pur- 
sued with such vigor by the pioneers of the science in America. 
The great progress in our knowledge of the morphology and 
physiology of plants during the last quarter of this century has 
changed the whole problem of elementary instruction in botany, 
and led to almost universal dissatisfaction with the old method 
jf secondary instruction in this subject. It is now generally 
ognized that a study of the lower plants, like the algae, fungi, 
jrworts, mosses, and ferns should form a part of a course of 

condary education in botany. 
To meet this end a number of books have sprung into exist - 

ice during the past few years. If the need for some guid- 
ance in the selection of topics, and an outline of the character 
of the study, could be met by nn??ibe?' alone of books, this want 
would be fully met in the new treatises recently published, and 
there would be no place for the present book. But a judicious 
selection of a few forms to illustrate function, process, and 
relationship throughout the wide range of plant life, and the 
training in logical methods of induction, and accuracy of draw- 
ing conclusions, is vastly more important in "its influence on 
the character of the pupil, even though he forget all about the 
plants studied, than the handling' -of. -a g^eat variety of objects, 
and the drawing of haphazard conclusions, which are left to the 
pupil in a large number of cases by the methods pursued in 
many of the recent elementary works, 

iii 



IV PREFACE. 

For several years the author has been deeply interested in the 
teaching of elementary botany, and has had an opportunity to 
study methods in a practical way, in having charge of the in- 
struction of a large class of beginners, the majority of whom 
had never studied the subject before. One of the great diffi- 
culties encountered in attempting to introduce the study of the 
lower plants is the fact that these plants are in most cases en- 
tirely unknown to the pupil. The difficulty does not lie in the 
attempt to introduce the study of unknown objects. But it lies 
rather in the attempt to study the lower plants, at the outset, in 
a more or less thorough manner, to learn their characters, rela- 
tionships, etc., in order to group them into their natural orders. 
This is attempting too much for the young beginner, to whom 
these plants are totally unfamiliar objects. 

The method followed in this book has been thoroughly tested 
in practical work. It is to first study some of the life processes 
of plants, especially those which illustrate the fundamental prin- 
ciples of nutrition, assimilation, growth, and irritability. In 
studying each one of these topics, plants are chosen, so far as 
possible, from several of the great groups. Members of the 
lower plants as well as of the higher plants are employed, in order 
to show that the process is fundamentally the same in all plants. 
Then another process is studied in a similar way, using so far as 
possible, especially where the lower plants are concerned, the 
same plant. In this way the mind is centered on this process, 
and the discovery to the pupil that it is fundamentally the same 
in such widely different plants arouses a keen interest not only 
in the plants themselves, but in the method which attends the 
discovery of this general principle. In the study of the life 
processes, the topics can be arranged so that they show progres- 
sion of function. 

At the same time it is well for the teacher to select for this 
study of the life processes those plants which represent well the 
great groups, and show gradual progression of form and struc- 
ture, and also those which arc easily obtained. 

A second period of the sessiofl can then be devoted to study- 



PREFA CE. V 

ing a few representatives of the different groups of the algae, 
fungi, liverworts, mosses, ferns, and the higher plants. This 
should be done with special reference to form, reproduction, 
general classification, progression, and retrogression of parts or 
organs, in passing from the lower to the higher plants. In 
taking up this study of representative forms now, if a wise selec- 
tion has been made in dealing with the life processes, the same 
plant can be used here in most cases. These plants now are 
familiar to the pupil, and the mind can be centered on form, 
organs, reproduction, relationship, etc. In this study of gen- 
eral morphology it is very important that a careful study be 
made of some of the lower plants, and of the ferns. Here the 
sexual organs are well formed, and the processes of reproduc- 
tion can be more easily observed. In the higher plants the 
sexual organs are very much reduced, and the processes more 
difficult to observe. It is only through a study of the lower 
plants that we are able to properly interpret the floral structures, 
and the sexual organs of the spermatophytes, and to rid our- 
selves of the erroneous conceptions which the prevalent method 
of elementary instruction has fixed so firmly on the lay mind. 

A third period of the elementary course may be employed in 
studying special morphology of the higher plants. Even here 
it seems to the author wise that the "analysis" of plants 
should be deferred until after a general notion of the characters 
and habit of several of the important families has been obtained. 
The pupil may be told the names of the several plants used as 
examples, and emphasis can be laid on ordinal and generic 
characters, which can then be recognized in many plants with- 
out resort to a key. The matter of determining the names of 
plants by the old method can, if desired, be pursued to greater 
advantage after this critical study of relationships has been made, 
even though the pupil may pursue it independently at a later time. 

In the study of plants one should not lose sight of the value 
of observing plants in their natural surroundings. If judiciously 
pursued it forms at once a means of healthful recreation, of com- 
munion with the very soul of nature, and of becoming ac- 



VI 



PKEF.l ( '/■:. 



quainted with the haunts, the lives, the successes and failures of 
plants ; the influences of soil, moisture, and other environ- 
mental conditions upon plants, and, what is also important, the 
influence which plants exert upon their environment. Classes 
may be taken into the field, at different seasons of the year, to 
observe flower and bud formation, pollenation, seed production, 
seed distribution, germination of seeds and nutrition of the 
embryo, protection of plants against foes and extremes of 
weather ; the relationships of plants in colonies, and their dis- 
tribution in plant formations, etc. In all this study a knowl- 
edge of some of the lower plants is important. 

It is not intended that the matter in the book should be mem- 
orized for the purpose of recitations. It should be used as a 
guide to the practical work, and as a reference book. The para- 
graphs arranged in coarse print are intended in general to indi- 
cate the studies which will serve as the basis for the practical 
work by the student. In most cases the material for these 
studies can be quite easily obtained and the laboratory work is 
not difficult. The paragraphs in fine print are intended to fur- 
ther illustrate the subject by discussion and illustration of the 
more difficult phases of each topic. Some of these can be made 
the basis for demonstrations by the teacher before the class, and 
all will serve as a convenient means of getting at the important 
reference matter by the student in a single book. Suggestions 
on the study and the taking of notes, etc., by the student are 
given in the appendix. 

Acknowledgments. — The author desires here to express his 
gratefulness to his associates m the botanical department of Cor- 
nell University who have read the manuscript and have made 
useful suggestions (Messrs. E, J, Durand, B. ML Duggar, K. M. 
Wilgand, and Professor W. W. Rowlee). Valuable suggestions 
were also given by Dr, J. C. Arthur, of Purdue University, who 
kindly read the chapters on physiology, and by Professor W, F. 
Ganong, o\ Smith College, who read some o\ the chapters on 
ecology and the tables on the homologies of the gymnosperms 
and angiosperms. 



PREFACE. Vll 

Illustrations. — The large majority of the illustrations are new, 
and were made with especial reference to the method of treatment 
followed in the text. Most of the photographs were made by 
the author. Others were contributed by Professor P. H. MH1, 
of the Alabama Polytechnic Institute, Auburn, Ala.; Professor 
Rowlee, Cornell University ; Mr. H. J. Webber, Washington, 
D. C. ; by the New Jersey Geological Survey through the courtesy 
of Mr. Gifford Pinchot, of New York ; by Mr. B. M. Duggar, 
Cornell University, and Mr. Herman von Schrenk, of the Mis- 
souri Botanical Garden. 

Many of the drawings, especially those of microscopic objects, 
were made by the author ; others by Mr. H. Hasselbring, Cor- 
nell University, and Dr. Bertha Stoneman, now professor of 
botany in the Huguenot College, Wellington, Cape Colony, 
South Africa. The drawings to illustrate the gross characters of 
plants were made by Mr. W. G. Holdsworth, Michigan Agri- 
cultural College; Mr. Joseph Bridgham, Providence, R. I.; 
Messrs. W, C. Furlong and W. C. Baker, Cornell University ; 
and a few by Miss Edna Porter, Buffalo, N. Y., and by Mrs. E. L. 
Nichols and Mrs. J. G. Needham, Cornell University. Pro- 
fessor Chas. A. Davis kindly furnished the sketches from which 
the drawings of the transformed trillium flower were made. 

Other illustrations have been obtained from the following 
sources: from the author's Study of the Biology of Ferns, 
through the courtesy of the Macmillan Co.; and from the 
Annals of Botany, Jahrbiicher fiir wissenschaftliche Botanik, 
Flora, Botanical Gazette, Vines' Student's Text Book of Botany, 
and Warming's Botany. 

Above all the author is under great obligations to Professors 
Ikeno and Hi rase, of the Imperial ^University of Japan, Tokio, 
for their unparalleled courtesy in sending drawings of the sperma- 
tozoids, and of fertilization, in cycas and gingko, in advance of 
their publication. 

Cornell University, June, 1898. 



CONTENTS. 

(References are to paragraphs.) 

CHAPTER I. 

PROTOPLASM. 

The plant spirogyra, 4. Chlorophyll bands in spirogyra, 5. 
The spirogyra thread consists of cylindrical threads end to 
end, 6. Protoplasm, 7. Cell-sap in spirogyra, 8. Reaction 
of protoplasm to certain reagents, 9. Earlier use of the 
term protoplasm, 11. Protoplastn in miicor, 12. Mycelium 
of mucor, 13. Appearance of the protoplasm, 14. Move- 
ment of the protoplasm in mucor, 15. Test for protoplasm, 
16. Protoplasm in nitella, 17. Form of nitella, 18. Inter- 
node of nitella, 19. Cyclosis in nitella, 20. Test for proto- 
plasm, 21. Protoplasm in one of the higher plants, 22. 
Movement of protoplasm in the higher plants, 23. Move- 
ment of protoplasm in cells of staminal hair of spiderwort, 
24. Cold retards the movement, 25. Protoplasm occurs in 
the living parts of all plants, 26 page 1 

CHAPTER II. 

ABSORPTION, DIFFUSION, OSMOSE. 

Osmose in spirogyra, 30. Turgescence, 31. Experiment with 
beet in salt and sugar solutions, 32. Osmose in the cells of 
the beet, 34. The coloring matter in the cell-sap does not 
readily escape from the living protoplasm of the beet, 35. 
The coloring matter escapes from dead protoplasm, 36. 
Osmose experiments with leaves, 37. Absorption by root- 
hairs, 39. Cell-sap a solution of certain substances, 40. 
Diffusion through an animal membrane, 41. Importance of 

these physical processes in plants, 44 page 13 

ix 



X CONTENTS. 

CHAPTER III. 

ABSORPTION OF LIQUID NUTRIMENT. 

Formula for solution of nutrient materials, 46. Plants take 
liquid food from the soil, 50. How food solutions are car- 
ried into the plant, 51. How the root-hairs get the watery 
solutions from the soil, 52. Plants cannot remove all the 
moisture from the soil, 53. Acidity of root-hairs, 56. . .page 22 

CHAPTER IV. 

TURGESCENCE. 

Turgidity of plant parts, 58. Restoration of turgidity in shoots, 
59. Tissue tensions, 61. Longitudinal tissue tension, 62. 
Transverse tissue tension, 65 page 28 

CHAPTER V. 

ROOT PRESSURE. 

Root pressure may be measured, 67. Experiment to demon- 
strate root pressure, 68 page 31 

CHAPTER VI. 

TRANSPIRATION. 

Loss of water from excised leaves, 71. Loss of water from 
growing plants, 72. Water escapes from the surfaces of 
living leaves in the form of water vapor, 73. Experiment 
to compare loss of water in a dry and a humid atmosphere, 
74. The loss of water is greater in a dry than in a humid 
atmosphere, 75. How transpiration takes place, 76. Struc- 
ture of a leaf, 79. Epidermis of the leaf, 80. Soft tissue 
of the leaf, 81. Stomata, 82. The living protoplasm re- 
tards the evaporation of water from the leaf, 83. Action of 
the stomata, 84. Transpiration may be in excess of root 
pressure, 85. Negative pressure, 86. Lifting power of 
transpiration, 87. Root pressure may exceed transpiration, 
88. Injuries caused by excessive root pressure, 89. Dem- 
onstration of stomates and intercellular spaces, 92 page 33 



CONTENTS. XI 

CHAPTER VII. 

PATH OF MOVEMENT OF LIQUIDS IN PLANTS. 

Place the cut ends of leafy shoots in a solution of some red dye, 
94. These solutions color the tracts in the stem and leaves 
through which they flow, 95. Structure of the fibro-vascu- 
lar bundles, 9S. Woody portion of the bundle, 99. Bast 
portion of the bundle, 100. Cambium region of the bundle, 
101. Longitudinal section of the bundle, 102. Vessels or 
ducts, 103. Sieve tubes, 105. Fibro-vascular bundle in In- 
dian corn, 107. Rise of water in the vessels, 108. Synopsis 
of tissues, 110 page 42 

CHAPTER VIII. 

DIFFUSION OF GASES. 

Gas given off by green plants in the sunlight, in. What this 
gas is, 117. Oxygen given off by green land plants also, 
118. Absorption of carbon dioxide, 119. The gases are 
exchanged in the plants, 122. A chemical change of the 
gas takes place within the plant cell, 123. Gases as well as 
water can diffuse through the protoplasmic membrane, 124 

page 49 

CHAPTER IX. 

RESPIRATION. 

Oxygen from the air consumed during germination of seed, 127. 
Carbon dioxide given off during germination, 128. Respi- 
ration is necessary for growth, 130. Energy set free during 
respiration, 132. Respiration in a leafy plant, 133. Respi- 
ration in fungi, 134. Respiration in plants in general, 135. 
Respiration a breaking-down process, 136. Detailed result 
of the above experiment, 137. Another way of performing 
the experiment, 138. Intramolecular respiration, 139.. page 54 

CHAPTER X. 

THE CARBON FOOD OF PLANTS. 

Starch formed as a result of carbon conversion, 141. Iodine 
used as a test for starch, 142. Schimper's method of testing 



Xll CONTENTS. 

for the presence of starch, 143. Green parts of plants form 
starch when exposed to the light, 147. Starch is formed 
only in the green parts of plants, 148. Translocation of 
starch, 149. Stanch in other parts of plants than the leaves, 
151. Form of starch grains, 153 page 59 

CHAPTER XI. 

CHLOROPHYLL AND FORMATION OF STARCH. 

Fungi cannot form starch, 155. Etiolated plants cannot convert 
carbon, 156. Chlorophyll and chloroplasts, 157. Form of 
the chlorophyll bodies, 158. Chlorophyll is a pigment which 
resides in the chloroplast, 159. Chlorophyll absorbs energy 
from sunlight for carbon conversion, 160. Rays of light 
concerned in carbon conversion, 161. Starch grains formed 
in the chloroplasts, 162. Carbon conversion in other than 
green plants, 164. Influence of light on the movement of 
chlorophyll bodies, 165 page 65 

CHAPTER XII. 

nutrition; members of the plant body. 

Nutrition of liverworts, 167. Riccia, 167. Marchantia, 168. 
Frullania, 169. Nutrition in the mosses, 170. The plant 
body, 171. Members of the plant body, 172. Stem series, 
173. Leaf series, 174. The root, 175 page 70 

CHAPTER XIII. 

GROWTH. 

Growth in mucor, 177. Formation of the gonidia, 178. The 
gonidia absorb water and increase in size before germinat- 
ing, 179. How the gonidia germinate, 180. The germ tube 
branches and forms the mycelium, 181. Growth in length 
takes place only at the end of the thread, 1S2. Proto- 
plasm increases by assimilation of nutrient substances, 183. 
Growth of roots, 184. Roots of the pumpkin, 185. The 
region of elongation, 186. Movement of the region of the 
greatest elongation, 187. Formative region, 188. Growth 
of the stem, 189. Force exerted by growth, 190. Grand 
period of growth, 191, Energy of growth, 193. Nutation, 
194 page 75 



CONTENTS, Xlll 

CHAPTER XIV. 

IRRITABILITY. 

Influence of the earth on the direction of growth, 197. Influ- 
ence of light on growth, 199. Influence of light on the di- 
rection of growth, 200. Diaheliotropism, 201. Epinasty 
and hyponastv, 202. Leaves with a fixed diurnal position, 
203. Importance of these movements, 204. Influence of 
light on the structure of the leaf, 205. Movement influ- 
enced by contact, 206. Sensitive plants, 207. Movement in 
response to stimuli, 20S. Transmission of the stimulus, 209. 
Cause of the movement, 210. Paraheliotropism of the 
leaves of the sensitive plant, 211. Sensitiveness of insec- 
tivorous plants, 212. Hydrotropism, 213. Temperature, 
214 page 82 



PART II. 

MORPHOLOGY. 

CHAPTER XV. 

SPIROGYRA. 

Form of spirogyra, 220. Multiplication of the threads, 221. 
How some of the threads break, 222. Conjugation of spiro- 
gyra, 223. How the threads conjugate or join, 225. How 
the protoplasm moves from one cell to another, 226. The 
zygospores, 227. Life cycle, 228. Fertilization, 229. Sim- 
plicity of the process, 230. Position of the plant spirogyra, 
231 page 93 

CHAPTER XVI. 

CEDOGONIUM. 

Form of oedogonium, 235. Fruiting stage of cedogonium, 236. 
Sexual organs of oedogonium; oogonium and egg y 237. 
Dwarf male plants, 238. Antheridium, 239. Zoospore 
stage of oedogonium, 240. Asexual reproduction, 241. Sex- 
ual reproduction, 242. Antheridia, 242. Oogonia, 243. 
CEdogonium compared with spirogyra, 244. Position of 
oedogonium, 245. Relatives of oedogonium, 246 page 99 



xiv CONTENTS. 

CHAPTER XVII. 

v.w CHERIA, 

Zoogonidia of vauchcria, 248. Sexual reproduction in vau- 
cheria, 249. Vaucheria sessilis, the sessile vaucheria, 250. 
Sexual organs of vaucheria, Antheridium, 251. Oogonium, 
252. Fertilization, 253. The twin vaucheria (V. geminata), 
254. Vaucheria compared with spirogyra, 255 page 109 

CHAPTER XVIII. 

CO] EOCHiE IK. 

The shield-shaped coleochaete, 257. Fruiting stage of coleo- 
ch.vte, 258. Zoospore stage, 250. Asexual reproduction, 
260, Sexual reproduction, oogonium, 261; antheridium, 
262. Sporocarp, 263, Comparative table for spirogyra, 
vaucheria, cedogonium. and coleochiete, 264 page no 

CHAPTER XIX. 

BROWN ANP RED AXGiB, 

Brown algSC (phfieophycea), 266. Form and occurrence of fucus, 
Structure of the conceptacles, 20S. Fertilization. 209. 
The red algae, 270. Gracillaria, 271. Rhabdonia, 272. 
Principal groups of alga\ 27 3 page 115 

CHAPTER XX. 
fungi; moulds; water moulds; downy mildews. 

Muc< Asexual reproduction. 276, Sexual stage. 277. 

Gemms, 278, Water moulds (saprolegnia), 270. Anpear- 

of the saproleg Sporangia oi saprolegnia, 

281. Zoogonidia of saprolegnia, :^:. Sexual reproduction 

of sapn 53 Downy mildews, 285 pace 120 

CHAPTER XXI. 

\ ... 

Wheat rus graminis), 289. leleutospores of the 

t-rust too. s rm. 

DO on the barberry 



CONTENTS. XV 

293. How the cluster-cup stage was found to be a part of 
the wheat rust, 293^/. Uredospores can produce successive 
crops, 294. Teleutospores the last stage in the season, 295. 
How the fungus gets back from the wheat to the barberry, 
296. Synopsis of life history of wheat rust, 297. Sac fungi, 
299. Fruit bodies of the willow mildew, 300. Asci and 
ascospores, 301. The sac fungi or ascomycetes, 302. Clas- 
sification of the fungi, 304 page 129 

CHAPTER XXII. 

LIVERWORTS. 

Riccia, 307. Form of the floating riccia (R. fluitans), 307. Form 
of the circular riccia (R. crystallina), 308. Sexual organs, 
309. Archegonia, 310. Antheridia, 311. Embryo, 312. 
Sporogonium of riccia, 313. A new phase in plant life, 314 
Riccia compared with coleochaete, cedogonium, etc., 315. 
Marchantia, 316. Antheridial plants, 317. Archegonial 
plants, 319 page 140 

CHAPTER XXIII. 

liverworts {continued). 

Sporogonium of marchantia, 320. Spores and elaters, 321. 
Sporophyte of marchantia compared with riccia, 322. 
Sporophyte dependent on the gametophyte for its nourish- 
ment, 323. Development of the sporogonium, 324. Em- 
bryo, 325. How marchantia multiplies, 326. Buds or 
gemmae of marchantia, 327. Leafy-stemmed liverworts, 
328. Frullania, 329. Porella, 330. Sporogonium of a foliose 
liverwort, 331 . page 149 

CHAPTER XXIV. 



Mnium, 334. The fruiting moss plant, 336. The male and fe- 
male moss plants, 337. Sporogonium, 338. Structure of 
the moss capsule, 339. Development of the sporogonium, 
342. Protonema of the moss, 343. Table showing relation 
of gametophyte and sporophyte in the liverworts and 
mosses, 344 , , page 158 



XVI CONTENTS. 



CHAPTER XXV. 



The Christmas fern, 346. Fruit dots, 347. Sporangia, 348. 
Structure of a sporangium, 349. Opening of the sporan- 
gium and dispersion of the spores, 351. How does the 
opening and snapping of the sporangium take place? 352. 
The movement of the sporangium can take place in old and 
dried material, 354. The common polopody, 356. Other 
ferns, 357. Opening of the leaves of ferns. 358. Longevity 
of ferns, 359. Budding of ferns, 360. The fern plant is*a 
sporophyte, 363. Is there a gametophyte phase in ferns? 
364 page 165 



CHAPTER XXVI. 

FERNS {concluded}. 

Gametophyte of ferns, 365. Sexual stage of ferns, 365. Spores, 
367. Germination of the spores, 368. Protonema, 369. 
Prothallium, 370. Sexual organs of ferns, 371. Antheridia, 
372. Archegonia, 373. Sporophyte, 374. Embryo, 374. 
Comparison of ferns with liverworts and mosses, 375 . .page 176 

CHAPTER XXVII. 

HORSETAILS. 

The field equisetum, 380. Fertile shoot, 380. Sporangia, 381. 
Spores, 382. Sterile shoot of the common horsetail, 383. 
The scouring rush or shave grass, 384. Gametophyte of 
equisetum, 385 page 1S7 

CHAPTER XXVIII. 

CLUB MOSSES. 

The clavate lycopodium, 387. Fruiting spike of Lycopodium 
clavatum, 388. Lycopodium lucidulum, 389. Bulbils on 
Lycopodium lucidulum, 390. The little club mosses, 392. 
Sporangia, macrospores and microspores, 393. Male pro- 
thallia, 394. Female prothallia, 395. Embryo, 396. .. .page 191 



CONTENTS. XVI 1 

CHAPTER XXIX. 

QUILLWORTS. 

Sporangia of isoetes, 398. Male prothallia, 401. Female pro- 

thallia, 402. Embryo, 403 page 196 

CHAPTER XXX. 

COMPARISON OF FERNS AND THEIR RELATIONS. 

Comparison of selaginella and isoetes with the ferns, 404. Gen- 
eral classification of ferns, 407. Table showing relation of 
gametophyte and sporophyte in the pteridophyta, 408. -page 199 

CHAPTER XXXI. 

GYMNOSPERMS. 

The white pine, 409. General aspect of the white pine, 409. 
The long shoots of the pine 410. The dwarf shoots of the 
pine, 411. Spore-bearing leaves of the pine, 412. Male 
cones or male flowers, 413. Microspores of the pine, or 
pollen grains, 414. Form of the mature female cone, 415. 
Form of a scale of the female flower, 417. Ovules or macro- 
sporangia of the pine, 418. Pollenation, 419. Female pro- 
thallium of the pine, 422. Archegonia, 423. Male prothal- 
lia, 424. Farther growth of the male prothallium, 425. 
Fertilization, 426. Homology of the parts of the female 
cone, 427 page 202 

CHAPTER XXXII. 

FARTHER STUDIES ON GYMNOSPERMS. 

Cycas, 428. Female prothallium of cycas, 429. Microspores or 
pollen of cycas, 431. The gingko tree, 432. Spermatozoids 
in some gymnosperms, 434. The sporophyte in the gymno- 
sperms, 435. The gametophyte has become dependent on 
the sporophyte, 436. Gymnosperms are naked seed plants, 
437. Classification of gymnosperms, 438. Table showing 
homologies of sporophyte and gametophyte in the pine, 
439 page 214 



XV111 CONTENTS. 

CHAPTER XXXIII. 

MORPHOLOGY OF THE ANGIOSPERMS. TRILLIUM; DENTARIA. 

Trillium, 440. General appearance, 440. Parts of the flower, 
calyx, 441. Corolla, 442. Androecium, 443. The stamen a 
sporophyll, 444. Gyncecium, 445. Transformation of the 
flower of trillium, 446. Dentaria, 447. General appear- 
ance, 447. Parts of the flower, 448 page 221 

CHAPTER XXXIV. 

GAMETOPHYTE AND SPOROPHYTE OF ANGIOSPERMS. 

Male prothallium of angiosperms, 450. Macrospore and em- 
bryo-sac, 453. Embryo-sac is the young female prothal- 
lium, 445. Fertilization, 456. Fertilization in plants is 
fundamentally the same as in animals, 457. Embryo, 458. 
Endosperm the mature female prothallium, 459. Seed, 460. 
Perisperm, 461. Presence or absence of endosperm in the 
seed, 462. Sporophyte is prominent and highly developed, 
463. The gametophyte once prominent has become degen- 
erate, 464. Synopsis of members of the sporophyte in 
angiosperms, 467. Table showing homologies of sporo- 
phyte and gametophyte in angiosperms, 468 page 228 

CHAPTER XXXV. 

MORPHOLOGY OF THE NUCLEUS AND SIGNIFICANCE OF 
GAMETOPHYTE AND SPOROPHYTE. 

Direct division of the nucleus, 470. Indirect division of the nu- 
cleus, 471. Chromatin and linin of the nucleus, 472. The 
chromatin skein, 473. Chromosomes, nuclear plate, and 
nuclear spindle, 474. The number of chromosomes usually 
the same in a given species throughout one phase of the 
plant, 474<?. When fertilization takes place the number of 
chromosomes is doubled in the embryo, 474^. Reduction of 
the number of chromosomes in the nucleus, 475. Signifi- 
cance of karyokinesis and reduction, 476. The gametophyte 
may develop directly from the tissue of the sporophyte, 477. 
The sporophyte may develop directly from the tissue of the 
gametophyte, 478. Perhaps there is not a fundamental dif- 
ference between the gametophyte and sporophyte, 479. page 239 



CONTENTS. XIX 

LESSONS ON PLANT FAMILIES. 
CHAPTER XXXVI. 

RELATIONSHIPS SHOWN BY FLOWER AND FRUIT. 

Importance of the flower in showing kinships among the higher 
plants, 480. Arrangement of flowers, 482. The fruit, 485 

page 247 

CHAPTER XXXVII. 

MONOCOTYLEDONS. 

(For lessons and topics see synopsis at close of the lessons.) 
Classification, 4S6. Species, 486. Genus, 487. Genus trillium, 
4S8. Genus erythronium, 489. Genus lilium, 490. Family 
liliaceae, 491. Floral formula, 492. Cohesion and adhe- 
sion, 493. Floral diagram, 494 page 251 

CHAPTER XXXVIII. 
MONOCOTYLEDONS {concluded) 258 

CHAPTER XXXIX. 

DICOTYLEDONS 262 

CHAPTER XL. 
DICOTYLEDONS {continued) 265 

CHAPTER XLI. 
DICOTYLEDONS {continued) 273 

CHAPTER XLII. 
DICOTYLEDONS {concluded) 283 

CHAPTER XLIII. 

OUTLINE OF TWENTY LESSONS IN THE ANGIOSPERMS 294 



XX CONTENTS. 



PART III. 

ECOLOGY. 

INTRODUCTION. page 300 

CHAPTER XLIV. 

winter buds; growth of woody shoots; leaf arrangement. 

Winter buds and how the young leaves are protected, 564. 
Twigs and buds of the horse-chestnut, 365. Leaf scars, 566. 
Lateral buds, 507. Hud leaves, 56S Opening of the buds 
in the spring, 569, Growth in thickness of woody stems, 
571. Difference in the firmness of the woody rings, 575. 
Annual rings in woody stems. 576. Phyllotaxy or arrange- 
ment of leaves, 579 P a ge 302 

CHAPTER XLV. 

SEEDLINGS. 

The common garden bean. 5S4. The castor-oil bean, 5S5. How 
the embryo gets out of a pumpkin seed, 5S6. Arisctma 
588. Germination of the seed of ** jack-in-the- 
pulpit," 5SS. How the embryo backs out of the seed, 5S9. 
How the first leaf appears, 591. The first leaf of " jack-in- 
the pulpit " is a simple one, 592 page 307 

CHAPTER XLVI. 

FURTHER STUDIES ON NUTRITION. 

\ trition in lem: Spirodela polyrrhiza. 505. Nutrition 

in wolffia, 5 / . Nutrition in lichens, 597. Nitrogen 

rs, ; How clovers, peas, and other legumes 

gather 1 A Fungal or bacterial organism in 

thes, :bercles, 600. How the organism cets in the 

s of the legumes. 601. The r ganisi -<:milates 

its host. 602. Mycorhiza, 603. Nutrition 

of the dodder, 605. Carr plants, 606. Nutrition of 

" . page 314 



CONTENTS. xxi 

CHAPTER XLVII. 

FURTHER STUDIES ON NUTRITION {concluded). 

Nutrition of moulds, 608. Nutrition of parasitic fungi, 609. 
Nutrition of the larger fungi, 610. Studies of mushrooms, 
613. Form of the mushroom, 613. Fruiting surface of the 
mushroom, 614. How the mushroom is formed, 615. He- 
ware of the poisonous mushrooms, 617. Wood-destroying 
fungi, 619 page 322 

CHAPTER XLVIII. 

DIMORPHISM OF FERNS. 

Dimorphism in the leaves of ferns, 624. The sensitive fern, 
625. Transformation of the fertile leaves of onoclea to 
sterile ones, 626. The sporangia decrease as the fertile leaf 
expands, 62S. The ostrich fern, 629. Dimorphism in tropi- 
cal ferns, 630 page 340 

CHAPTER XLIX. 

FORMATION OF EARLY SPRING FLOWERS. 

Trillium, 631. The adder tongue (erythronium), 633. Indian 

turnip, 634 ' page 347 

CHAPTER L. 

HETEROSPORY. POLLENATION. 

Origin of heterospory and the necessity for pollenation, 639. 
Both kinds of sexual organisms on the same prothallium, 
639. Cross fertilization in monoecious prothallia, 640. Ten- 
dency toward dioecious prothallia, 641. The two kinds of 
sexual organs on different prothallia, 642. Permanent sep- 
aration of the sexes by different amounts of nutriment 
supplied the spore, 643. Heterospory, 644 In the pterido- 
phytes water serves as the medium for conveying the 
sperm cell to the female organ. 645. In the higher plants a 
modification of the prothallium is necessary, 6^6. Pollena- 
tion ^ 649. Self pollenation or close pollenation, 649. Wind 
pollenation, 650 Pollenation by insects, 651. Pollenation 
of the bluet, 653. Pollenation of the primrose, 654. Pol- 



XXll CONTENTS. 

lenation of the skunk's cabbage, 655. Spiders have discov- 
ered this curious relation of the flowers and insects, 657. 
Pollenation of jack-in-the-pulpit, 658. Pollenation of or- 
chids, 660. Pollenation of canna, 664 page 351 

CHAPTER LI. 

SEED DISTRIBUTION. 

Means for dissemination of seed, 672. The prickly lettuce, 676. 
The wild lettuce, 677. The milk-weed or silk-weed, 678. 
The virgin's bower, 680 page 368 

CHAPTER LII. 

STRUGGLE FOR OCCUPATION OF LAND. 

Retention of made soil, 681. Vegetation of sand dunes, 683. 

Reforestation of lands, 0S4. Beauty of old fields, 6S9. .page 374 

CHAPTER LIII. 

SOIL FORMATION IN ROCKY REGIONS AND IN MOORS. 

Lichens, 690. Lichens are among the pioneers in soil forma- 
tion, 691. Other plants of rocky regions, 692. Filling of 
ponds by plants, 694. A plant atoll, 695. Topography of 
the atoll moor, 696. A floating inner zone, 698. How was 
the atoll formed ? 700. A black-spruce moor, 703. Fall of 
the trees of the marginal zone when the windbreak was 
removed, 704. Dying of the spruce of the central area, 705. 
Other morainic moors, 70S. The bald cypress (taxodium), 
711 P a £ e :^ s " 

CHAPTER LIV. 

ZONAL DISTRIBUTION OF PLANTS. 

On the margins of lakes and ponds, 712. On the banks of a 

stream, 716 page 400 

CHAPTER LV. 

PLANT COMMUNITIES; SEASONAl chances. 

Plants of widely different groups may exist in the same com- 
munity, 720. Seasonal succession in plant communities, 



CONTENTS. xxill 

722. The landscape a changing panorama, 725. Refoliation 
of bare forests in the spring, 726. The summer tints are 
more subdued, 728. Autumn colors, 729. Fall of the leaf, 
730 page 410 

CHAPTER LVI. 

ADAPTATION OF PLANTS TO CLIMATE. 

Some characteristics of desert vegetation. 731. Some plants of 
temperate regions possess characters of desert vegetation, 
735. Alpine plants with desert characters, 737. Low stat- 
ure of alpine plants a protection against wind and cold, 738. 
Some plants of swamps and moors present characters of 
arctic or desert vegetation, 739. Hairs on young leaves 
protect against cold, 740 page 419 



BOTANY. 

CHAPTER I. 

PROTOPLASM.* 

1. In the study of plant life and growth, it will be found 
convenient first to inquire into the nature of the substance 
which we call the living material of plants. For plant growth, 
as well as some of the other processes of plant life, are at bottom 
dependent on this living matter. This living matter is called in 
general protoplasm. 

2. In most cases protoplasm cannot be seen without the 
help of a microscope, and it will be necessary for us here to em- 
ploy one if we wish to see protoplasm, and to satisfy ourselves 
by examination that the substance we are dealing with is 
protoplasm. 

3. We will find it convenient first to examine protoplasm in 
some of the simpler plants ; plants which from their minute size 
and simple structure are so transparent that when examined with 
the microscope the interior can be seen. 

For our first study we will take a plant known as spirogyra, 
though there are a number of others which would serve the pur- 
pose quite as well, and may quite as easily be obtained for 
study. 

*For apparatus, reagents, collection and preservation of material, etc., see 
Appendix. 



PHYSIOLOGY. 



Protoplasm in spirogyra. 

4. The plant spirogyra. — This plant is found in the water 
of pools, ditches, ponds, or in streams of slow-running water. 
It is green in color, and occurs in loose mats, usually floating 
near the surface. The name "pond-scum" is sometimes given 
to this plant, along with others which are more or less closely 
related. It is an alga, and belongs to a group of plants known 
as algcB. If we lift a portion of it from the water, we see that 
the mat is made up of a great tangle of green silky threads. 
Each one of these threads is a plant, so that the number con- 
tained in one of these floating mats is very great. 

Let us place a bit of this thread tangle on a glass slip, and 
examine with the microscope and we will see certain things about 
the plant which are peculiar to it, and which enable us to dis- 
tinguish it from other minute green water plants. We shall 
also wish to learn what these peculiar parts of the plant are, in 
order to demonstrate the protoplasm in the plant.* 

5. Chlorophyll bands in spirogyra. — We first observe the 
presence of bands ; green in color, the edges of which are 
usually very irregularly notched. These bands course along in 
a spiral manner near the surface of the thread. There may be 
one or several of these spirals, according to the species which 
we happen to select for study. This green coloring matter of 
the band is chlorophyll, and this substance, which also occurs in 
the higher green plants, will be considered in a later chapter. 
At quite regular intervals in the chlorophyll band are small 
starch grains, grouped in a rounded mass enclosing a minute 
body, the pyrenoid, which is peculiar to many algae. 

6. The spirogyra thread consists of cylindrical cells end to 
end. — Another thing which attracts our attention, as we examine 
a thread of spirogyra under the microscope, is that the thread is 

* If spirogyra is forming fruit some of the threads will be lying parallel in 
pairs, and connected with short tubes. In some of the celfs there will be 
found rounded or oval bodies known as zygospores. These may be seen in 
fig. 86, and will be described in another part of the book. 



PROTOPLASM. 



3 




L 



made up of cylindrical segments or compartments placed end to 
end. We can see a distinct separating line be- 
tween the ends. Each one of these segments or 
compartments of the thread is a cell, and the 
boundary wall is in the form of a cylinder with 
closed ends. 

7. Protoplasm. — Having distinguished these 
parts of the plant we can look for the protoplasm. 
It occurs within the cells. It is colorless (i.e., 
hyaline) and consequently requires close observa- 
tion. Near the center of the cell can be seen a 
rather dense granular body of an elliptical or 
irregular form, with its long diameter transverse 
to the axis of the cell in some species; or trian- 
gular, or quadrate in others. This is the nucleus. 
Around the nucleus is a granular layer from which 
delicate threads of a shiny granular substance 
radiate in a starlike manner, and terminate in the 
chlorophyll band at one of the pyrenoids. A 
granular layer of the same substance lines the 
inside of the cell wall, and can be seen through 
the microscope if it is properly focussed. This 
granular substance in the cell is protoplasm. 

8. Cell-sap in spirogyra. — The greater part of 
the interior space of the cell, that between the 
radiating strands of protoplasm, is occupied by 
a watery fluid, the " cell-sap." 

9. Reaction of protoplasm to certain reagents. 
— We can employ certain tests to demonstrate 
that this granular substance which we have seen 
is protoplasm, for it has been found, by repeated 
experiments with a great many kinds of plants, 
that protoplasm gives a definite reaction in re- 
sponse to treatment with certain substances called 
reagents. Let us mount a few threads of the 
spirogyra in a drop of a solution of iodine, and observe the 



Thread of spiro- 
gyra, showing long 
cells, chlorophyll 
band, nucleus, 
strands of proto- 
plasm, and the 
granular wall layer 
of protoplasm 



PHYSIOLOGY. 



results with the aid of the microscope. The iodine gives a 
yellowish-brown color to the protoplasm, and it can be more 
distinctly seen. The nucleus is also much more prominent 
since it colors deeply, and we can perceive within the nucleus 
one small rounded body, sometimes more, the nucleolus. The 
iodine here has stained the living protoplasm. The proto- 
plasm, however, in a living condition will resist for a time some 

other reagents, 



as we shall see 
if we attempt 
to stain it with 
a one per cent 
aqueous solu- 
tion of a dye 
known as eosin. 
Let us mount a 
few living 
tli reads in such 
a solution of 
eosin, and after 
a time wash off 




Fig. 2. 



Fig- 3- 



Cell of spirogyra before treat- Cell of spirogyra after treatment +Uf* ctain TVip» 
merit with iodine. with alcohol and iodine. Hie Sldlll. 1 lie 

protoplasm remains uncolored. Now let us place these threads 
for a short time, two or three minutes, in strong alcohol, which 
kills the protoplasm. Then mount them in the eosin solution. 
The protoplasm now takes the eosin stain. After the proto- 
plasm has been killed we note that the nucleus is no longer 
elliptical or angular in outline, but is rounded. The strands of 
protoplasm are no longer in tension as they were when alive. 

10. Let us now take some fresh living threads and mount 
them in water. Place a small drop of dilute glycerine on the 
slip at one side of the cover glass, and with a bit of filter paper 
at the other side draw out the water. The glycerine will flow 
under the cover glass and come in contact with the spirogyra 
threads. Glycerine absorbs water promptly. Being in contact 
with the threads it draws water out of the cell cavity, thus caus- 



PROTOPLASM. 



5 



ing the layer of protoplasm which lines the inside of the cell 
wall to collapse, and separate from the wall, drawing the 
chlorophyll band 
inward toward the 
center also. The 
wall layer of proto- 
plasm can now be 
more distinctly 
seen and its gran- 
ular character ob- 
served. 

We have thus 
employed three 
tests to demon- 
strate that this sub- 
stance with which 
we are dealing 
shows the reac- 
tions which we 
know by experi- 
ence to be given 
by protoplasm. We therefore conclude that this colorless and 
partly granular, slimy substance in the spirogyra cell is proto- 
plasm, and that when we have performed these experiments, 
and noted carefully the results, we have seen protoplasm. 




Fig. 4. 
Cell of spirogyra before 
treatment with glycerine. 




Cells of spirogyra after treatment 
with glycerine. 



11. Earlier use of the term protoplasm. — Early students of the living 
matter in the cell considered it to be alike in substance, but differing in 
density; so the term protoplasm was applied to all of this living matter. The 
nucleus was looked upon as simply a denser portion of the protoplasm, and 
the nucleolus as a still denser portion. Now it is believed that the nucleus is 
a distinct substance, and a permanent organ of the cell. The remaining por- 
tion of the protoplasm is now usually spoken of as the cytoplasm. 

In spirogyra then the cytoplasm in each cell consists of a layer which lines 
the inside of the cell wall, a nuclear layer, which surrounds the nucleus, and 
radiating strands which connect the nucleus and wall layers, thus suspending 
the nucleus near the center of the cell. But it seems best in this elementary 
study to use the term protoplasm in its general sense. 



PHYSIOLOGY. 



Protoplasm in mucor. 

12. Let us now examine in a similar way another of the 
simple plants with the special object in view of demonstrating 
the protoplasm. For this purpose we may take one of the plants 
belonging to the group of fungi. These plants possess no 
chlorophyll. One of several species of mucor, a common 
mould, is readily obtainable, and very suitable for this study.* 

13. Mycelium of mucor. — A few days after sowing in some 
gelatinous culture medium we find slender, hyaline threads, which 
are very much branched, and, radiating from a central point, form 
circular colonies, if the plant has not been too thickly sown, as 
shown in fig. 6. These threads of the fungus form the myce- 
lium. From these characters of the plant, which we can readily 
see without the aid of a microscope, we note how different it is 
from spirogyra. 

To examine for protoplasm let us lift carefully a thin block of 
gelatine containing the mucor threads, and mount it in water on 
a glass slip. Under the microscope we see only a small portion 
of the branched threads. In addition to the absence of chlo- 
rophyll, which we have already noted, we see that the myce- 
lium is not divided at short intervals into cells, but appears 
like a delicate tube with branches, which become successively 
smaller toward the ends. 

14. Appearance of the protoplasm. — Within the tube-like 
thread now note the protoplasm. It has the same general ap- 
pearance as that which we noted in spirogyra. It is slimy, or 
semi-fluid, partly hyaline, and partly granular, the granules con- 
sisting of minute particles (the ?mcrosomes). While in mucor the 
protoplasm has the same general appearance as in spirogyra, its 
arrangement is very different. In the first place it is plainly 

* The most suitable preparations of mucor for study are made by growing 
the plant in a nutrient substance which largely consists of gelatine, or, better, 
agar-agar, a gelatinous preparation of certain seaweeds. This, after the 
plant is sown in it, should be poured into sterilized shallow glass plates, 
called Petrie dishes. 






PROTOPLASM. 



continuous throughout the tube. We do not sec the prominent 
radiations of strands around a large nucleus, but still the proto- 







m 




Fig 6. 
Colonies of mucor. 

plasm does not fill the interior of the threads. Here and there 
are rounded clear spaces termed vacuoles, which are filled with 
the watery fluid, cell-sap. The nuclei in mucor are very mi- 
nute, and cannot be seen except after careful treatment with 
special reagents. 

15 Movement of the protoplasm in mucor. — While exam- 
ining the protoplasm in mucor we are likely to note streaming 
movements. Often a current is seen flowing slowly down one 
side of the thread, and another flowing back on the other side, 
or it may all stream along in the same direction. 

16. Test for protoplasm. — Now let us treat the threads with 
a solution of iodine. The yellowish-brown color appears which 
is characteristic of protoplasm when subject to this reagent. 



8 PHYSIOLOGY. 

If we attempt to stain the living protoplasm with a one per 
cent aqueous solution of eosin it resists it for a time, but if we 
first kill the protoplasm with strong alcohol, it reacts quickly to 
the application of the eosin. If we treat the living threads 
with glycerine the protoplasm is contracted away from the wall, 
as we found to be the case with spirogyra. While the color, 




Fig. 7- 
Thread of mucor, showing protoplasm and vacuoles. 

form and structure of the plant mucor is different from spiro- 
gyra, and the arrangement of the protoplasm within the plant 
is also quite different, the reactions when treated by certain re- 
agents are the same. We are justified then in concluding that 
the two plants possess in common a substance which we call 
protoplasm. 

Protoplasm in nitella. 

17. One of the most interesting plants for the study of one remarkable 
peculiarity of protoplasm is Nitella* This plant belongs to a small group 
known as stoneworts. They possess chlorophyll, and, while they are still 
quite simple as compared with the higher plants, they are much higher in the 
scale than spirogyra or mucor. 

18. Form of nitella — A common species of nitella is Nitella Jlexilis. 
It grows in quiet pools of water. The plant consists of a main axis, in the 
form of a cylinder. At quite regular intervals arc whorls of several smaller 
thread-like outgrowths, which, because of their position, are termed " leaves, 1 ' 
though they are not true leaves. These arc branched in a characteristic fash- 
ion at the tip. The main axis also branches, these branches arising in the axil 
of a whorl, usually singly. The portions of the axis where the whorls arise 
are the nodes. Each node is made up of a number of small cells definitely 
arranged. The portion oi the axis between two adjacent whorls is an inter- 



PROTOPLASM. 9 

node. These internodes are peculiar. They consist of but a single "cell," 
and are cylindrical, with closed ends. They are sometimes 5-10 cm. long. 

19. Internode of nitella. — For the study of an internode of nitella, a 
small one, near the end, or the ends of one of the " leaves " is best suited, 
since it is more transparent. A small 
portion of the plant should be placed 
on the glass slip in water with the 
cover glass over a tuft of the branches 
near the growing end. Examined with 
the microscope the green chlorophyll bodies, which 
form oval or oblong discs, are seen to be very numer- 
ous. They lie quite closely side by side and form in 
perfect rows along the inner surface of the wall. One 
peculiar feature of the arrangement of the chlorophyll 
bodies is that there are two lines, extending from one 
end of the internode to the other on opposite sides, 
where the chlorophyll bodies are wanting. These are 
known as neutral lines. They run parallel with the 
axis of the internode, or in a more or less spiral 
manner as shown in fig. 9. 

20. Cyclosis in nitella. — The chlorophyll bodies 

are stationary on the inner surface of the wall, but 

if the microscope be properly focussed just beneath 

this layer we notice a rotary motion of particles in 

the protoplasm. There are small granules and quite 

large masses of granular matter which glide slowly 

along in one direction on a given side of the neutral 

line. If now we examine the protoplasm on the other 

side of the neutral line, we see that the movement is 

in the opposite direction. If we examine this move- lg ', ' . ,, 

rr Portion of plant nitella. 

ment at the end of an internode the particles are seen 

to glide around the end from one side of the neutral line to the other. So 
that when conditions are favorable, such as temperature, healthy state of the 
plant, etc., this gliding of the particles or apparent streaming of the proto- 
plasm down one side of the " cell," and back upon the other, continues in 
an uninterrupted rotation, or cyclosis. There are many nuclei in an internode 
of nitella, and they move also. 

21. Test for protoplasm. — If we treat the plant with a solution of iodine 
we get the same reaction as in the case of spirogyra and mucor. The proto- 
plasm becomes yellowish brown. 

22. Protoplasm in one of the higher plants. — We now wish 
to examine, and test for, protoplasm in one of the higher plants. 





IO PHYSIOLOGY. 

Young or growing parts of any one of various plants — the petioles 
of young leaves, or young stems of growing plants — are suitable 
for study. Tissue from the pith of corn (Zea mays) in young 

shoots just back of the 
growing point or quite 
near the joints of older but 
growing corn stalks fur- 
Fig. 9 nishes excellent material. 
Cydosis in niteiia. jf we should place part 
of the stem of this plant under the microscope we should find 
it too opaque for observation of the interior of the cells. This 
is one striking difference which we note as we pass from the low 
and simple plants to the higher and more complex ones ; not 
only in general is there an increase of size, but also in general 
an increase in thickness of the parts. The cells, instead of lying 
end to end or side by side, are massed together so that the parts 
are quite opaque. In order to study the interior of the plant 
we have selected it must be cut into such thin layers that the 
light will pass readily through them. 

For this purpose we section the tissue selected by making with 
a razor, or other very sharp knife, very thin slices of it. These 
are mounted in water in the usual way for microscopic study. In 
this section we notice that the cells are polygonal in form. 
This is brought about by mutual pressure of all the cells. The 
granular protoplasm is seen to form a layer just inside the wall, 
which is connected with the nuclear layer by radiating strands 
of the same substance. The nucleus does not always lie at the 
middle of the cell, but often is near one side. If we now kill 
with alcohol and treat with iodine the characteristic yellowish- 
brown color appears. So we conclude here also that this sub- 
stance is identical with the living matter in the other very differ- 
ent plants which we have studied. 

23. Movement of protoplasm in the higher plants. — Cer- 
tain parts of the higher plants are suitable objects for the study 
of the so-called streaming movement of protoplasm, especially 
the delicate hairs, or thread-like outgrowths, such as the silk of 



PROTOPLASM, I I 

corn, or the delicate staminal hairs of some plants, like those of 
the common spiderwort, tradescantia, or of the tradescantias 
grown for ornament in greenhouses and plant conservatories. 

Sometimes even in the living cells of the corn plant which we 
have just studied, slow streaming or gliding movements of the 
granules are seen along the strands of protoplasm where they 
radiate from the nucleus. 

24. Movement of protoplasm in cells of the staminal hair of 
" spiderwort." — A cell of one of these hairs from a stamen of a 
tradescantia grown in glass houses is shown in fig. 10. The 




*lg. IO. 

Cell from stamen hair of tradescantia showing movement of the protoplasm, 



nucleus is quite prominent, and its location in the cell varies con- 
siderably in different cells and at different times. There is a 
layer of protoplasm all around the nucleus, and from this the 
strands of protoplasm extend outward to the wall layer. The 
large spaces between the strands are, as we have found in other 
cases, filled with the cell-sap. 

An entire stamen, or a portion of the stamen, having several hairs attached, 
should be carefully mounted in water. Care should be taken that the room be 
not cold, and if the weather is cold the water in which the preparation is 
mounted should be warm. With these precautions there should be little diffi- 
culty in observing the streaming movement. 

The movement is detected by observing the gliding of the 
granules. These move down one of the strands from the nucleus 
along the wall layer, and in towards the nucleus in another 
strand. After a little the direction of the movement in any one 
portion may be reversed. 

25. Cold retards the movement. — While the protoplasm is 
moving, if we rest the glass slip on a block of ice, the move- 
ment will become slower, or will cease altogether. Then if we 



12 PHYSIOLOGY. 

warm the slip gently, the movement becomes normal again. We 
may now apply here the usual tests for protoplasm. The result 
is the same as in the former cases. 

26. Protoplasm occurs in the living parts of all plants. — 

In these plants representing such widely different groups, we find 
a substance which is essentially alike in all. Though its arrange- 
ment in the cell or plant body may differ in the different plants 
or in different parts of the same plant, its general appearance 
is the same. Though in the different plants it presents, while 
alive, varying phenomena, as regards mobility, yet when killed 
and subjected to well known reagents the reaction is in general 
identical. Knowing by the experience of various investigators 
that protoplasm exhibits these reactions under given conditions, 
we have demonstrated to our satisfaction that we have seen proto- 
plasm in the simple alga, spirogyra, in the common mould, 
mucor, in the more complex stonewort, nitella, and in the cells 
of tissues of the highest plants. 

27. By this simple process of induction of these facts concerning 
this substance in these different plants, we have learned an im- 
portant method in science study. Though these facts and deduc- 
tions are well known, the repetition of the methods by which they 
are obtained on the part of each student helps to form habits of 
scientific carefulness and patience, and trains the mind to logical 
processes in the search for knowledge. 

28. While we have by no means exhausted the study of protoplasm, we can, 
from this study, draw certain conclusions as to its occurrence and appearance 
in plants. Protoplasm is found in the living and growing parts of all plants. 
It is a semi-fluid, or slimy, granular, substance ; in some plants, or parts of 
plants, the protoplasm exhibits a streaming or gliding movement of the gran- 
ules. It is irritable. In the living condition it resists more or less for some 
time the absorption of certain coloring substances. The water may be with- 
drawn by glycerine. The protoplasm may be killed by alcohol. When 
treated with iodine it becomes a yellowish-brown color. 



CHAPTER II. 

ABSORPTION, DIFFUSION, OSMOSE. 

29. We may next endeavor to learn how plants absorb 
water or nutrient substances in solution. There are several 
very instructive experiments, which can be easily performed, 
and here again some of the lower plants will be found useful. 

30. Osmose in spirogyra. — Let us mount a few threads of 
this plant in water for microscopic examination, and then draw 
under the cover glass a five per cent solution of ordinary table 
salt (NaCl) with the aid of filter paper. We shall soon see 
that the result is similar to that which was obtained when glycer- 
ine was used to extract the water from the cell-sap, and to con- 
tract the protoplasmic membrane from the cell wall. But the 
process goes on evenly and the plant is not injured. The proto- 
plasmic layer contracts slowly from the cell wall, and the move- 
ment of the membrane can be watched by looking through the 
microscope. The membrane contracts in such a way that all 
the contents of the cell are finally collected into a rounded or 
oval mass which occupies the center of the cell. 

If we now add fresh water and draw off the salt solution, 
we can see the protoplasmic membrane expand again, or move 
out in all directions, and occupy its former position against the 
inner surface of the cell wall. This would indicate that there is 
some pressure from within while this process of absorption is 
going on, which causes the membrane to move out against the 
cell wall. 

The salt solution draws water from the cell-sap. 'There 
is thus a tendency to form a vacuum in the cell, and the 
pressure on the outside of the protoplasmic membrane causes it 

13 



H 



PHYSIOLOGY. 



to move toward the center of the cell. When the salt solution 
is removed and the thread of spirogyra is again bathed with 
water, the movement of the water is inward in 
the cell. This would suggest that there is some 
substance dissolved in the cell-sap which does not 
readily filter out through the membrane, but draws 
on the water outside. It is this which produces 
the pressure from within and crowds the mem- 
brane out against the cell wall again. 



n/ >. 



Y : m 



n. 

Spiroeyra before 
placing in salt solu- 
tion. 




Fig. 13. 

Spirogyra from salt 
solution into water. 



Fig. 12. 
Spirogyra in 551 salt solution. 



31. Turgescence. — Were it not for the resistance which the 
cell wall offers to the pressure from within, the delicate proto- 



ABSORPTION, DIFFUSION, OSMOSE. 



*5 



plasmic membrane would stretch to such an extent that it would 
be ruptured, and the protoplasm therefore would be killed. If 
we examine the cells at the ends of the 
threads of spirogyra we will see in most 
cases that the cell wall at the free end is 
arched outward. 
T his is brought 
about by the press- 




Fig. 16. 

From salt solution placed in water. 
Figs. 14-16. — Osmosis in threads of mucor. 



Fig. 14. 

Before treatment with salt 

solution. 

lire from within 
upon the proto- After j^Lent with 
plasmic m e m - salt solution - 
brane which itself presses against 
the cell wall, and causes it to 
arch outward. This is beauti- 
fully shown in the case of threads 
which are recently broken. The cell wall is therefore elastic; 
it yields to a certain extent to the pressure from within, but a 
point is soon reached beyond which it will not stretch, and an 
equilibrium then exists between the pressure from within on the 
protoplasmic membrane, and the pressure from without by the 
elastic cell wall. This state of equilibrium in a cell is turges- 
cence, or such a cell is said to be turgescent, or iurgid. 

32. Experiment with beet in salt and sugar solutions. — 
We may now test the effect of a five per cent salt solution on a 
portion of the tissues of a beet or carrot. Let us cut several 
slices of equal size and about $mm in thickness. Immerse a 
few slices in water, a few in a five per cent salt solution and a 
few in a strong sugar solution. It should be first noted that all 
the slices are quite rigid when an attempt is made to bend them 
between the fingers. In the course of one or two hours or less, 



i6 



PHYSIOLOGY. 



if we examine the slices we will find that those in water remain, 
as at first, quite rigid, while those in the salt and sugar solutions 
are more or less flaccid or limp, and will readily bend by pres- 




Fig. 17. Fig. 18. Fig. 19. 

Before treatment with salt After treatment with salt From salt solution into water 
solution. solution. again. 

Figs. 17-19. — Osmosis in cells of Indian corn. 

sure between the fingers, the specimens in the salt solution, 
perhaps, being more flaccid than those in the sugar solution. 
The salt solution, we judge after our experiment with spirogyra, 






Fig. 20. 



Fig. 21 



Fig. 22. 



Rigid condition of fresh beet Limp condition after lying in Rigid again after lying again 

section. salt solution. in water. 

Pigs. 20-22. — Turgor and osmosis in slices of beet. 

withdraws some of the water from the cell-sap, the cells thus 
losing their turgidity and the tissues becoming limp or flaccid 
from the loss of water. 



ABSORPTION, DIFFUSION, OSMOSE. 



17 



33. Let us now remove some of the slices of the beet from 
the sugar and salt solutions, wash them with water and then im- 
merse them in fresh water. In the course of thirty minutes to 
one hour, if we examine them again, they will be found to have 
regained, partly or completely, their rigidity. Here again we 
infer from the former experiment with spirogyra that the sub- 
stances in the celi-sap now draw water inward ; that is, the 
diffusion current is inward through the cell walls and the proto- 
plasmic membrane, and the tissue becomes turgid again. 

34. Osmose in the cells of the beet. — We should now make a section of the 
fresh tissue of a red colored beet for examination with the microscope, and 
treat this section with the salt solution. Here we can see that the effect of the 
salt solution is to draw water out of the cell, so that the protoplasmic mem- 




Fig. 25. 
Later stage ot the same. 



Fig. 23. Fig. 24. 

Before treatment with salt After treatment with salt 
solution. solution. 

Figs. 23-25. — Cells from beet treated with salt solution to show osmosis and movement of 
the protoplasmic membrane. 

brane can be seen to move inward from the cell wall just as was observed in 
the case of spirogyra.- Now treating the section with water and removing 
the salt solution, the diffusion current is in the opposite direction, that is in- 



* We should note that the coloring matter of the beet resides in the cell- 
sap. It is in these colored cells that we can best see the movement take 
place, since the red color serves to differentiate well the moving mass from the 
cell wall. The protoplasmic membrane at several points usually clings tena- 
ciously so that at several places the membrane is arched strongly away from 
the cell wall as shown in fig. 24. While water is removed from the cell-sap, 
we note that the coloring matter does not escape through the protoplasmic 
membrane. 



1 8 PHYSIOLOGY. 

ward through the protoplasmic membrane, so that the latter is pressed outward 
until it comes in contact with the cell wall again, which by its elasticity soon 
resists the pressure and the cells again become turgid. 

35. The coloring matter in the cell-sap does not readily escape from the 
living protoplasm of the "beet. — The red coloring matter, as seen in the sec- 
tion under the microscope, does not escape from the cell-sap through the pro- 
toplasmic membrane . When the slices are placed in water, the water is not 
colored thereby. The same is true when the slices are placed in the salt or 
sugar solutions. Although water is withdrawn from the cell-sap, this coloring 
substance does not escape, or if it does it escapes slowly and after a consider- 
able time. 

36. The coloring matter escapes from dead protoplasm. — If, however, we 
heat the water containing a slice of beet up to a point which is sufficient to 
kill the protoplasm, the red coloring matter in the cell-sap filters out through 
the protoplasmic membrane and colors the water. If we heat a preparation 
made for study under the microscope up to the thermal death point we can 
see here that the red coloring matter escapes through the membrane into the 
water outside. This teaches that certain substances cannot readily filter 
through the living membrane of protoplasm, but that they can filter through 
when the protoplasm is dead. A very important condition, then, for the suc- 
cessful operation of some of the physical processes connected with absorption 
in plants is that the protoplasm should be in a living condition. 

37. Osmose experiments with leaves. — We may next take the leaves of 
certain plants like the geranium, coleus or other plant, and place them in 
shallow vessels containing water, salt, and sugar solutions respectively. The 
leaves should be immersed, but the petioles should project out of the water or 
solutions. Seedlings of corn or beans, especially the latter, may also be 
placed in these solutions, so that the leafy ends are immersed. After one or 
two hours an examination will show that the specimens in the water are still 
turgid. But if we lift a leaf or a bean plant from the salt or sugar solution, 
it will be found to be flaccid and limp. The blade, or lamina, of the leaf 
droops as if wilted, though it is still wet. The bean seedling also is flaccid, 
the succulent stem bending nearly double as the lower part of the stem is held 
upright. This loss of turgidity is brought about by the loss of water from the 
tissues, and judging from the experiments on spirogyra and the beet, we con- 
clude that the loss of turgidity is caused by the withdrawal of some of the 
water from the cell sap by the strong salt solution. 

38. Now if we wash carefully these leaves and seedlings, which have been 
in the salt and sugar solutions, with water, and then immerse them in fresh 
water for a few hours, they will regain their turgidity. Here again we are led 
to infer that the diffusion current is now inward through the protoplasmic 
membranes of all the living cells of the leaf, and that the resulting turgidity 
of the individual cells causes the turgidity of the leaf or stem. 



ABSORPTION, DIFFUSION, OSMOSE. 



19 



L 






39. Absorption by root hairs. — If we examine seedlings, 
which have been grown in a germinator or in the folds of paper 
or cloths so that the roots will be free from particles of soil, we 
will see near the growing point of the roots that the surface is 
covered with numerous slender, delicate, thread- 
like bodies, the root hairs. Let us place a portion 
of a small root containing some of these root 
hairs in water on a glass slip, and prepare it for 
examination with the microscope. We will see 
that each thread, or root hair, is a continuous 
tube, or in other words it is a single cell which 
has become very much elongated. The proto- 
plasmic membrane lines the wall, and strands of 
protoplasm extend across at irregular intervals, the 
interspaces being occupied by the cell-sap. 

We should now draw under the cover glass 
some of the five per cent salt solution. The 
protoplasmic membrane moves away from the cell 
wall at certain points, showing that plasmolysis is 
taking place, that is, the diffusion current is out- 
ward so that the cell-sap loses some of its water, 
and the pressure from the outside moves the 
membrane inward. We should not allow the salt 
solution to work on the root hairs long. It should 
be very soon removed by drawing in fresh water 
before the protoplasmic membrane has been 
broken at intervals, as is 
apt to be the case by the 
strong diffusion current ^^^/|K 
and the consequent 
strong pressure fro m 
without 
of protoplasm now moves 

outward as the diffusion current is inward, and soon regains its 
former position next the inner side of the cell wall. The 
root hairs then, like other parts of the plant which we have 



1 




Fig. 27. 
Root hair of corn 
Fig. 26. before and after 

The membrane Seedling of radish, showing root treatment with 5^ 

hairs. salt solution. 



20 PHYSIOLOGY. 

investigated, have the power of taking up water under press- 
ure. 

40. Cell-sap a solution of certain substances. — From these experiments we 
are led to believe that certain substances reside in the cell-sap of plants, which 
behave very much like the salt solution when separated from water by the 
protoplasmic membrane. Let us attempt to interpret these phenomena by 
recourse to diffusion experiments, where an animal membrane separates two 
liquids of different concentration. 

41. Diffusion through an animal membrane. — For this experiment we 
may use a thistle tube, across the larger end of which should be stretched and 
tied tightly a piece of a bladder membrane. A strong sugar solution (three 
parts sugar to one part water) is now placed in the tube so that the bulb is 
filled and the liquid extends part way in the neck of the tube. This is im- 
mersed in water within a wide-mouth bottle, the neck of the tube being sup- 
ported in a perforated cork in such a way that the sugar solution in the tube is 
on a level with the water in the bottle or jar. In a short while the liquid 
begins to rise in the thistle tube, in the course of several hours having risen 
several centimeters. The diffusion current is thus stronger through the mem- 
brane in the direction of the sugar solution, so that this gains more water than 
it loses. 

42. We have here two liquids separated by an animal membrane, water on 
the one hand which diffuses readily through the membrane, while on the other 
is a solution of sugar which diffuses through the animal membrane with diffi- 
culty. The sugar solution is also what is called a concentrated solution, i.e., 
it is more highly concentrated than water. The water, therefore, according 
to a general law which has been found to obtain in such cases, diffuses more 
readily through the membrane into the sugar solution, which thus increases in 
volume, and also becomes more dilute. The bladder membrane is what is 
sometimes called a diffusion membrane, since the diffusion currents travel 
through it. 

43. In this experiment then the bulk of the sugar solution is increased, and 
the liquid rises in the tube by this pressure above the level of the water in the 
jar outside of the thistle tube. The diffusion of liquids through a membrane 
is osmosis, and the membrane, since it permits one liquid to pass in one direc- 
tion more rapidly than in the other, is sometimes called a semipermeable 
membrane, 

44. Importance of these physical processes in plants. — Now if we recur 
to our experiment with spirogyra we find that exactly the same processes take 
place. The protoplasmic membrane is thf* diffusion membrane, or semiperme- 
able membrane, through which the diffusion takes place. The salt solution 
which is first used to bathe the threads of the plant is a more highly concen- 
trated solution than that of the cell sap within the cell. Water therefore is 



! 



ABSORPTION, DIFFUSION, OSMOSE. 21 

drawn out of the cell-sap, but the substances in solution in the cell-sap do not 
readily move out. As the bulk of the cell-sap diminishes the pressure from 
the outside pushes the protoplasmic membrane away from the wall. Now 
when we remove the salt solution and bathe the thread with water again, the 
cell-sap, being a more highly concentrated solution than water, diffuses 
with more difficulty and the diffusion current is inward, while the protoplasmic 
membrane moves out against the cell wall, and turgidity again results. Also 
in the experiments with salt and sugar solutions on the leaves of geranium, on 
the leaves and stems of the seedlings, on the tissues and cells of the beet and 
carrot, and on the root hairs of the seedlings, the same processes take place. 

These experiments not only teach us that in the protoplasmic membrane, the 
cell wall, and the cell-sap of plants do we have structures which are capable of 
performing these physical processes, but they also show that these processes are 
of the utmost importance to the plant ; not only in giving the plant the power 
to take up solutions of nutriment from the soil, but they serve also other pur- 
poses, as we shall see later. 



CHAPTER III. 

ABSORPTION OF LIQUID NUTRIMENT. 

45. We are now ready to inquire how plants obtain food 
from the soil or water. Chemical analysis shows that certain 
mineral substances are common constituents of plants. By 
growing plants in different solutions of these various substances it 
has been possible to determine what ones are necessary constitu- 
ents of plant food. While the proportion of the mineral ele- 
ments which enter into the composition of plant food may vary 
considerably within certain limits, the concentration of the solu- 
tions should not exceed certain limits. A very useful solution is 
one recommended by Sachs, and is as follows : 

46. Formula for solution of nutrient materials : 

Water iooo cc. 

Potassium nitrate 0.5 gr. 

Sodium chloride 0.5 " 

Calcium sulphate o. 5 ' ' 

Magnesium sulphate o. 5 * ' 

( 'alcium phosphate o. 5 " 

The calcium phosphate is only partly soluble. The solution which is not 
in use should be kept in a dark cool place to prevent the growth of minute 
algae. 

47. Several different plants are useful for experiments in water cultures, as 
peas, corn, beans, buckwheat, etc. The seeds of these plants may be germi- 
nated, after soaking them for several hours in warm water, by placing them 
between the folds of wet paper on shallow trays, or in the folds of wet cloth. 
The seeds should not be kept immersed in water after they have imbibed 
enough to thoroughly soak and swell them. At the same time that the seeds 
are placed in damp paper or cloth for germination, one lot of the soaked seeds 

22 



A BSORP TION NU TRIM EN T. 



23 



should be planted in good soil and kept under the same temperature condi- 
tions, for control. When the plants have germinated one series should be 
grown in distilled water, which possesses no plant food; another in the nutrient 
solution, and still another in the nutrient solution to which has been added a 
few drops of a solution of iron chloride or ferrous sulphate. There would 
then be four series of cultures which should be carried out with the same kind 
of seed in each series so that the comparisons can be made on the same species 
under the different conditions. The series should be numbered and recorded 
as follows : 

No. I, soil. 

No. 2, distilled water. 

No. 3, nutrient solution. 

No. 4, nutrient solution with a few drops of iron solution added. 

48. Small jars or wide -mouth bottles, or crockery jars, can be used for the 
water cultures, and the cultures are set up as follows : A cork which will just 
fit in the mouth of the bottle, or which can be supported by pins, is perforated 
so that there is room to insert the seedling, 
with the root projecting below into the liquid. 
The seed can be fastened in position by insert- 
ing a pin through one side, if it is a large one, 
or in the case of small seeds a cloth of a coarse 
mesh can be tied over the mouth of the bottle 
instead of using the cork. After properly set- 
ting up the experiments the cultures should be 
arranged in a suitable place, and observed from 
time to time during several weeks. In order to 
obtain more satisfactory results several dupli- 
cate series should be set up to guard against the 
error which might arise from variation in indi- 
vidual plants and from accident. Where there 
are several students in a class, a single series 
set up by several will act as checks upon one 
another. If glass jars are used for the liquid 
cultures they should be wrapped with black 
paper or cloth to exclude the light from the 
liquid, otherwise numerous minute algae are apt to grow and interfere with the 
experiment. Or the jars may be sunk in pots of earth to serve the same 
purpose. If crockery jars are used they will not need covering. 

49. For some time all the plants grow equally well, until the nutriment 
stored in the seed is exhausted. The numbers I, 3 and 4, in soil and nutri- 
ent solutions, should outstrip number 2, the plants in the distilled water. 
No. 4 in the nutrient solution with iron, having a perfect food, compares favor- 
ably with the plants in the soil. 




Fig. 28. 

Culture cylinder to show position of 
corn seedling 1 Hansen). 



24 



PHYSIOLOGY. 



50. Plants take liquid food from the soil. — From these ex- 
periments then we judge that such plants take up the food they 
receive from the soil in the form of a liquid, the elements being 
in solution in water. 

If we recur now to the experiments which were performed with 
the salt solution in producing plasmol.ysis in the cells of spirogyra, 
in the cells of the beet or corn, and in the root hairs of the corn 
and bean seedlings, and the way in which these cells become tur- 
gid again when the salt solution is removed and they are again 
bathed with water, we will have an explanation of the way in 
which plants take up nutrient solutions of food material through 
their roots. 

51. How food solutions are carried into the plant. — We can 




Fig. 29. 
SectioD ol corn root, showing rhizoids formed from elongated epidermal cells. 

Bee how the root hairs are able to take up solutions of plant food, 
and we must next turn our attention to the way in which these 



ABSORPTION NUTRIMENT. 2$ 

solutions are carried farther into the plant. We should make a 
section across the root of a seedling in the region of the root 
hairs and examine it with the aid of a mi< roscope. We here see 
thai the root hairs are formed by the elongation of certain of the 
surface cells of the root. These cells elongate perpendicularly to 
the root, and become ynm to 6mm Long. They are flexuous or 
irregular in outline and cylindrical, as shown in fig. 29. The 
end of the hair next the root fits in between the adjacent superfi- 
cial cells of the root and joins closely to the next deeper layer of 
cells. In studying the section of the young root we see that the 
root is made up of cells which lie closely side by side, each with 
its wall, its protoplasm and cell-sap, the protoplasmic membrane 
lying on the inside of each cell wall. 

52. In the absorption of the watery solutions of plant food by the root 
hairs, the cell-sap, being a more concentrated solution, gains some of the 
former, >ince the liquid of less concentration flows through the protoplasmic 
membrane into the more concentrated cell-sap, increasing the bulk of the lat- 
ter. This makes the root hairs turgid, and at the same time dilutes the cell- 
sap so that the concentration is not so great. The cells of the root lying in- 
side and close to the base of the root hairs have a cell-sap which is now more 
concentrated than the diluted cell-sap of the hairs, and consequently gain 
some of the food solutions from the latter, which tends to lessen the content 
of the root hairs and also to increase the concentration of the cell-sap of the 
same. This makes it possible for the root hairs to draw on the soil for more 
of the food solutions, and thus, by a variation in the concentration of the sub- 
stances in solution in the cell-sap of the different cells, the food solutions are 
carried along until they reach the vascular bundles, through which the solu- 
tions are carried to distant parts of the plant. Some believe that there is a 
rhythmic action of the elastic cell walls in these cells between the root hairs and 
the vascular bundles. This occurs in such a way that, after the cell becomes 
turgid, it contracts, thus reducing the size of the cell and forcing some of the 
food solutions into the adjacent cells, when by absorption of more food solu- 
tions, or water, the cell increases in turgidity again. This rhythmic action of 
the cells, if it does take place, would act as a pump to force the solutions 
along, and would form one of the causes of root pressure. 

53. How the root hairs get the watery solutions from the soil. — If we 
examine the root hairs of a number of seedlings which are growing in the soil 
under normal conditions, we shall see that a large quantity of soil readily 
clings to the roots. We should note also that unless the soil has been recently 
watered there is no free water in it ; the soil is only moist. We are curious 



26 



PHYSIOLOGY. 



to know how plants can obtain water from soil which is not wet. If we at- 
tempt to wash off the soil from the roots, being careful not to break away the 




Fig. 30. 
Root hairs of corn seedling with soil particles adhering closely. 

I it \\i root na ^ rs > we fi n d tnat small particles cling so tenaciously to 
'i ' I J J 'J the root hairs that they are not removed. Placing a few such 

root hairs under the microscope it appears as if here and there the root hairs 

were glued to the minute soil particles. 

54. If now we take some of the soil which is only moist, weigh it, and 
then permit it to become quite dry on exposure to dry air, and weigh again, 
we will find that it loses weight in drying. Moisture has been given off. 
This moisture, it has been found, forms an exceedingly thin film on the sur- 
face of the minute soil particles. Where these soil particles lie closely to- 
gether, as they usually do when massed together in the pot or elsewhere, this 
thin film of moisture is continuous from the surface of one particle to that of an- 
other. Thus the soil particles which are so closely attached to the root hairs 
connect the surface of the root hairs with this film of moisture. As the cell- 
sap of the root hairs draws on the moisture film with which they are in con- 
tact, the tension of this film is sufficient to draw moisture from distant parti- 
cles. ] n this way the roots are supplied with water in soil which is only 
moist. 

55. Plants cannot remove all the moisture from the soil. — If we now take 
a potted plant, or a pot containing a number of seedlings, place it in a moder- 
ately dry room, and do not add water to the soil it will be found in a few days 
that the plant is wilting. The soil if examined will appear quite dry to the 
sense of touch. Let us weigh some of this soil, then dry it by artificial 



ABSORPTION NUTRIMENT. 2*] 

heat, and weigh again. It has lost in weight. This has been brought about 
by driving oft* the moisture which still remained in the soil after the plant 
began to wilt. This teaches that while plants can obtain water from soil 
which is only moist or which is even rather dry, they are not able to withdraw 
all the moisture from the soil. 

56. Acidity of root hairs. — If we take a seedling which has 
been grown in a germinator, or in the folds of cloths or paper, 
so that the roots are free from the soil, and touch the moist root 
hairs to blue litmus paper, the paper becomes red in color where 
the root hairs have come in contact. This is the reaction for 
the presence of an acid substance, and indicates that the root 
hairs excrete certain acids. This acid property of the root hairs 
serves a very important function in the preparation of certain 
of the elements of plant food in the soil. Certain of the 
chemical compounds of potash, phosphoric acid, etc., become 
deposited on the soil particles, and are not soluble in water. 
The acid of the root hairs dissolves some of these compounds 
where the particles of soil are in close contact with them, and 
the solutions can then be taken up by the roots. 

57. This corrosive action of the roots can be shown by the well-known 
experiment of growing a plant on a marble plate which is covered by soil. 
After a few weeks, if the soil be washed from the marble where the roots 
have been in close contact, there will be an outline of this part of the root 
system. Several different acid substances are excreted from the roots of plants 
which have been found to redden blue litmus paper by contact. Experiments 
by Czapek, however, show that it is carbonic acid which has the power of 
dissolving these compounds, while the other acids excreted by the roots do 
not have this power. 



CHAPTER IV. 

TURGESCENCE. 

58. Turgidity of plant parts. — As we have seen by the 
experiments on the leaves, turgescence of the cells is one of the 
conditions which enables the leaves to stand out from the stem, 
and the lamina of the leaves to remain in an expanded position, 
so that they are better exposed to the light, and to the currents 
of air. Were it not for this turgidity the leaves would hang 
down close against the stem. 

59. Restoration of turgidity in shoots. — If we cut off a 
living stem of geranium, coleus, tomato, or " balsam," and allow 
the leaves to partly wilt so that the shoot loses its turgidity, it is 
possible for this shoot to regain turgidity. 'The end may be 
freshly cut again, placed in a vessel of water, covered with a bell 

jar and kept in a room where the temperature 
is suitable for the growth of the plant. The 
shoot will usually become turgid again from 
the water which is absorbed through the cut 
end of the stem and is carried into the leaves 
where the individual cells become turgid, and 
the leaves are again expanded. Such shoots, 
;iiid the excised lea\ es also, may often be made 
turgid again bv simply immersing them in 
water, as one of the experiments with the salt 
solution would teach. 




I he i in end of tin- sh< 



GO. Turgidity may In- restored more certainly and 
quickly in a partially wilted shoot in another way. 
ol may be inserted in a l tube as shown in fig, 31, the 



end of the tube around the stem <>i tin- plant being made air tight. The arm 

28 



TURGESCENCE. 29 

of the tube in which the stem is inserted is filled with water and the water is 
allowed to partly fill the other arm. Into this other arm is then poured 
mercury. The greater weight of the mercury causes such pressure upon the 
water that it is pushed into the stem, where it passes up through the vessels 
in the stems and leaves, and is brought more quickly and surely to the cells 
which contain the protoplasm and cell-sap, so that turgidity is more quickly 
and certainly attained. 

61. Tissue tensions. — Besides the turgescence of the cells of 
the leaves and shoots there are certain tissue tensions without 
which certain tender and succulent shoots, etc., would be limp, 
and would droop. There are a number of plants usually accessi- 
ble, some at one season and some at others, which may be used 
to illustrate tissue tension. 

62. Longitudinal tissue tension. — For this in early summer 
one may use the young and succulent shoots of the elder 
(sambucus); or the petioles of rhubarb during the summer and 
early autumn ; or the petioles of richardia. Petioles of cala- 
dium are excellent for this purpose, and these may be had at 
almost any season of the year from the greenhouses, and are 
thus especially advantageous for work during late autumn or 
winter. The tension is so strong that a portion of such a 
petiole 10-15^7// long is ample to demonstrate it. As we grasp 
the lower end of the petiole of a caladium, or rhubarb leaf, we 
observe how rigid it is, and how well it supports the heavy 
expanded lamina of the leaf. 

63. The ends of a portion of such a petiole or other object 
which may be used are cut off squarely. With a knife a strip 
from 2-ynm in thickness is removed from one side the full 
length of the object. This strip will now be found to be shorter 
than the larger part from which it was removed. The outer 
tissue then exerts a tension upon the petiole which tends to 
shorten it. Let us remove another strip lying next this one, 
and another, and so on until the outer tissues remain only upon 
one side. The object will now bend toward that side. Now 
remove this strip and compare the length of the strips removed 
with the central portion. They will be found to be much 



30 PHYSIOLOGY. 

shorter now. In other words there is also a tension in the tissue 
of the central portion of the petiole, the direction of which is 
opposite to that of the superficial tissue. The parts of the petiole 
now are not rigid, and they easily bend. These two longitudi- 
nal tissue tensions acting in opposition to each other therefore 
give rigidity to the succulent shoot. It is only when the indi- 
vidual cells of such shoots or petioles are turgid that these tissue 
tensions in succulent shoots manifest themselves or are promi- 
nent. 

64. To demonstrate the efficiency of this tension in giving support, let us 
take a long petiole of caladium or of rhubarb. Hold it by one end in a hori- 
zontal position. It is firm and rigid, and does not droop, or but little. Re- 
move all of the outer portion of the tissues, as described above, leaving only 
the central portion. Now attempt to hold it in a horizontal position by one 
end. It is flabby and droops downward because the longitudinal tension is 
removed. 

65. Transverse tissue tension. — To illustrate this one may 
take a willow shoot $-$cm in diameter and saw off sections 
about 2cm long. Cut through the bark on one side and peel it 
off in a single strip. Now attempt to replace it. The bark will 
not quite cover the wood again, since the ends will not meet. It 
must then have been held in transverse tension by the woody 
part of the shoot. 



CHAPTER V. 

ROOT PRESSURE. 

66. It is a very common thing to note, when certain shrubs 
or vines are pruned in the spring, the exudation of a watery 
fluid from the cut surfaces. In the case of the grape vine this 
has been known to continue for a number of days, and in some 
cases the amount of liquid, called " sap," which escapes is con- 
siderable. In many cases it is directly traceable to the activity 
of the roots, or root hairs, in the absorption of water from the 
soil. For this reason the term root pressure is used to denote 
the force exerted in supplying the water from the soil. 

67. Root pressure may be measured. — It is possible to 
measure not only the amount of water which the roots will raise 
in a given time, but also to measure the force exerted by the 
roots during root pressure. It has been found that root pressure 
in the case of the nettle is sufficient to hold a column of water 
about 4.5 meters (15 ft.)high(Vines), while the root pressure of the 
vine (Hales, 1721) will hold a column of water about 10 meters 
(36.5 ft.) high, and the birch (Betula lutea) (Clark, 1873) has a 
root pressure sufficient to hold a column of water about 25 meters 
(84.7 ft.) high. 

68. Experiment to demonstrate root pressure. — By a very simple method 
this power of root pressure may be demonstrated. During the summer season 
plants in the open may be used if it is preferred, but plants grown in pots are 
also very serviceable, and one may use a potted begonia or balsam, the latter 
being especially useful. The plants are usually convenient to obtain from the 
greenhouses, to illustrate this phenomenon. The stem is cut off rather close to 
the soil and a long glass tube is attached to the cut end of the stem, still con- 
nected with the roots, by tne use of rubber tubing as shown in figure 32, and a 

31 



32 



PHYSIOLOGY. 



very small quantity of water may be poured in to moisten the cut end of the 
stem. In a few minutes the water begins to rise in the glass tube. In some 
cases it rises quite rapidly, so that the column of water can 
readily be seen to extend higher and higher up in the tube when 
observed at quite short intervals. The height of this column 
of water is a measure of the force exerted by the roots. The 
pressure force of the roots may be measured also by deter- 
mining the height to which it will raise a column of mercury. 

69. In either case where the experiment is con- 
tinued for several days it is noticed that the column 
of water or of mercury rises and falls at different 
times during the same day, that is, the column stands 
at varying heights; or in other words the root 
pressure varies during the day. With some plants 
it has been found that the pressure is greatest at 
certain times of the day, or at certain seasons of the 
year. Such variation of root pressure exhibits what 
Experiment to i s termed a periodicity, and in the case of some 

show root press- L J 

lire (Detmer). plants there is a daily periodicity; while in others 
there is in addition an annual periodicity. With the grape vine 
the root pressure is greatest in the forenoon, and decreases from 
12-6 p.m., while with the sunflower it is greatest before 10 
a.m., when it begins to decrease. Temperature of the soil is 
one of the most important external conditions affecting the 
activity of root pressure. 




CHAPTER VI. 

TRANSPIRATION. 

70. We should now inquire if all the water which is taken up 
in excess of that which actually suffices for turgidity is used in the 
elaboration of new materials of construction. We notice when a 
leaf or shoot is cut away from a plant, unless it is kept in quite 
a moist condition, or in a damp, cool place, that it becomes flac- 
cid, and droops. It wilts, as we say. The leaves and shoot 
lose their turgidity. This fact suggests that there has been a 
loss of water from the shoot or leaf. It can be readily seen that 
this loss is not in the form of drops of water which issue from the 
cut end of the shoot or petiole. What then becomes of the water 
in the cut leaf or shoot ? 

71. Loss of water from excised leaves. — Let us take a hand- 
ful of fresh, green, rather succulent leaves, which are free from 
water on the surface, and place them under a glass bell jar, which 
is tightly closed below but which contains no water. Now we 
will place this in a brightly lighted window, or in sunlight. In 
the course of fifteen to thirty minutes we notice that a thin film 
of moisture is accumulating on the inner surface of the glass jar. 
After an hour or more the moisture has accumulated so that it 
appears in the form of small drops of condensed water. We 
should set up at the same time a bell jar in exactly the same way 
but which contains no leaves. In this jar there will be no con- 
densed moisture on the inner surface. We thus are justified in 
concluding that the moisture in the former jar comes from the 
leaves. Since there is no visible water on the surfaces of the 
leaves, or at the cut ends, before it may have condensed there, 

33 



34 PHYSIOLOGY, 

we infer that the water escapes from the leaves in the form of 
water vapor, and that this water vapor, when it comes in contact 
with the surface of the cold glass, condenses and forms the mois- 
ture film, and later the drops of water. The leaves of these cut 
shoots therefore lose water in the form of water vapor, and thus 
a loss of turgidity results. 

72. Loss of water from growing plants. — Suppose we now 
take a small and actively growing plant in a pot, and cover the 
pot and the soil with a sheet of rubber cloth w r hich fits tightly 
around the stem of the plant (or the pot and soil may be enclosed 
in a hermetically sealed vessel) so that the moisture from the soil 
cannot escape. Then place a bell jar over the plant, and set in 
a brightly lighted place, at a temperature suitable for growth. 
In the course of a few minutes on a dry day a moisture film forms 
on the inner surface of the glass, just as it did in the case of the 
glass jar containing the cut shoots and leaves. Later the mois- 
ture has condensed so that it is in the form of drops. If we have 
the same leaf surface here as we had with the cut shoots, we will 
probably find that a larger amount of water accumulates on the 
surface of the jar from the plant that is still attached to its 
roots. 

73. Water escapes from the surfaces of living leaves in the 
form of water vapor. — This living plant then has lost water, 
which also escapes in the form of water vapor. Since here there 
are no cut places on the shoots or leaves, we infer that the loss 
of water vapor takes place from the surfaces of the leaves and 
from the shoots. It is also to be noted that, while this plant is 
losing water from the surfaces of the leaves, it does not wilt or 
lose its turgidity. The roots by their activity and pressure sup- 
ply water to take the place of that which is given off in the form 
of water vapor. This loss of water in the form of water vapor by 
plants is transpiration, 

74. Experiment to compare loss of water in a dry and a 
humid atmosphere. — We should now compare the escape of 
water from the leaves of a plant < overed by a bell jar, as in the 
last experiment, with that which takes place when the plant is 



TRANSP1AA TJ OX. 35 

exposed in a normal way in the air of the room or in the open. 
To do this we should select two plants of the same kind growing 
in pots, and of approximately the same leaf surface. The potted 
plants are placed one each on the arms of a scale. One of the 
plants is covered in this position with a bell jar. With weights 
placed on the pan of the other arm the two sides are balanced. 
In the course of an hour, if the air of the room is dry, moisture 
has probably accumulated on the inner surface of the glass jar 
which is used to cover one of the plants. This indicates that 
there has here been a loss of water. But there is no escape of 
water vapor into the surrounding air so that the weight on this 
arm is practically the same as at the beginning of the experiment. 
We see, however, that the other arm of the balance has risen. 
We infer that this is the result of the loss of water vapor from the 
plant on that arm. Now let us remove the bell jar from the other 
plant, and with a cloth wipe off all the moisture from the inner 
surface, and replace the jar over the plant. We note that the 
end of the scale which holds this plant is still lower than the 
other end. 

75. The loss of water is greater in a dry than in a humid 
atmosphere. — This teaches us that while water vapor escaped 
from the plant under the bell jar r the air in this receiver soon 
became saturated with the moisture, and thus the farther escape 
of moisture from the leaves was checked. It also teaches us an- 
other very important fact, viz. , that plants lose water more rapidly 
through their leaves in a dry air than in a humid or moist atmos- 
phere, We can now understand why it is that during the very 
hot and dry part of certain days plants often wilt, while at night- 
fall, when the atmosphere is more humid, they revive. They lose 
more water through their leaves during the dry part of the day, 
other things being equal, than at other times. 

76. How transpiration takes place. — Since the water of 
transpiration passes off in the form of water vapor we are led to 
inquire if this process is simply evaporation of water through the 
surface of the leaves, or whether it is controlled to any appreci- 
able extent by any condition of the living plant. An experiment 



36 PHYSIOLOGY. 

which is instructive in this respect we will find in a comparison 
between the transpiration of water from the leaves of a cut shoot, 
allowed to lie unprotected in a dry room, and a similar cut shoot 
the leaves of which have been killed. 

77. Almost any plant will answer for the experiment. For this purpose I 
have used the following method. Small branches of the locust (Robinia 
pseudacacia), of sweet clover (Melilotus alba), and of a heliopsis were 
selected. One set of the shoots was immersed for a moment in hot water near 
the boiling point to kill them. The other set was immersed for the same 
length of time in cold water, so that the surfaces of the leaves might be well 
wetted, and thus the two sets of leaves at the beginning of the experiment 
would be similar, so far as the amount of water on their surfaces is con- 
cerned. All the shoots were then spread out on a table in a dry room, the 
leaves of the killed shoots being separated where they are inclined to cling 
together. In a short while all the water has evaporated from the surface of 
the living leaves, while the leaves of the dead shoots are still wet on the sur- 
face. In six hours the leaves of the dead shoots from which the surface 
water had now evaporated were beginning to dry up, while the leaves of the 
living plants were only becoming flaccid. In twenty -four hours the leaves 
of the dead shoots were crisp and brittle, while those of the living shoots were 
only wilted. In twenty -four hours more the leaves of the sweet clover and 
of the heliopsis were still soft and flexible, showing that they still contained 
more water than the killed shoots which had been crisp for more than a 
day. 

78. It must be then that during what is termed transpiration the living 
plant is capable of holding back the water to some extent, which in a dead 
plant would escape more rapidly by evaporation. It is also known that a 
body of water with a surface equal to that of a given leaf surface of a plant 
loses more water by evaporation during the same length of time than the 
plant loses by transpiration. 

79. Structure of a leaf. — We are now led to inquire why it is 
that a living leaf loses water less rapidly than dead ones, and 
why less water escapes from a given leaf surface than from an 
equal surface of water. To understand this it will be necessary 
to examine the minute structure 'of a leaf. For this purpose we 
will select the leaf of an ivy, though many other leaves will 
answer equally well. From a portion of the leaf we should make 
very thin cross sections with a razor or other sharp instrument. 
These sections should be perpendicular to the surface of the leaf 



TRANSPIRA TIOA\ 



37 




and should be then mounted in water for microscopic examina- 
tion.* 

80. Epidermis of the leaf. — In this section we see that the 
green part of the leaf is bordered on what are its upper and 
lower surfaces by a row of cells which 
possess no green color. The walls of 
the cells of each row r have nearly par- 
allel sides, and the cross walls are per- 
pendicular. These cells form a single 
layer over both surfaces of the leaf and 
are termed the epidermis. Their walls 
are quite stout and the outer walls are 
cuticularized. 

81. Soft tissue of the leaf. — The 
cells which contain the green chloro- 
phyll bodies are arranged in two dif- , Flg ; 3 . 3 ' . r . . 

r J ° Section through ivy leaf showing 

ferent Ways. Those On the Upper Side communication between stomateand 

J L x the large intercellular spaces ol the 

of the leaf are usually long and pris- leaf ; stoma dosed. 
matic in form and lie closely parallel to each other. Because of 
this arrangement of these cells they are termed the palisade cells, 
and form what is called the palisade layer. The other green 

cells, lying below, 
vary greatly in size in 
different plants and to 
some extent also in the 
same plant. Here we 
notice that they are 
elongated, or oval, or 
somewhat irregular in 
form. The most striking peculiarity, however, in their arrange- 
ment is that they are not usually packed closely together, but each 
cell touches the other adjacent cells only at certain points. This 
arrangement of these cells forms quite large spaces between them, 
the intercellular spaces. If we should examine such a section of 
a leaf before it is mounted in w T ater we would see that the inter- 




Fig. 34- 
Stoma open. 

Figs. 34, 35.— Section through stomata of ivy leaf. 



Fig. 35- 
Stoma closed. 



* Demonstrations may be made with prepared sections of leaves. 



38 



PHYSIOLOGY. 




Fig. 36. 
Portion of epidermis of ivy, showing irregular epidermal cells, sto 
and guard cells. 



cellular spaces are not filled with water or cell-sap, but are filled 
with air or some gas. Within the cells, on the other hand, we 
find the cell-sap and the protoplasm. 

82. Stomata. — If we examine carefully the row of epidermal 
cells on the under surface of the leaf, we will find here and there 
a peculiar arrangement of cells shown at figs. 33—35. This 

opening 

through the 

e p i de rmal 

layer is a 

stoma. The 

Jr^s, l\^ KS J^(( cells which 

~~\\ v^-^ == ^" < ^ft \) immediately 

\ ^^\ /&*J( ff surround the 

openings are 

the guard 

a cells. The 

form of the 

guard cells can be better seen if we tear a leaf in such a way as 
to strip off a short piece of the lower epidermis, and mount this 
in water. The guard cells are nearly crescent shaped, and the 
stoma is elliptical in outline. The epidermal cells are very 
irregular in outline in this view. We should also note that while 
the epidermal cells contain no chlorophyll, the guard cells do. 

83. The living protoplasm retards the evaporation of water from the 
leaf. — If we now take into consideration a few facts which we have learned 
in a previous chapter, with reference to the physical properties of the living 
cell, we will be able to give a partial explanation of the comparative- slowness 
with which the water escapes iron) the leaves. The inner surfaces of the cell 
walls are lined with the membrane of protoplasm, and within this is the cell- 
sap. These cells have become turgid by the absorption of the water which 
has passed up to them from the roots. While the protoplasmic membrane of 

the cells does not readily permit the water to filter through, yet it is saturated 
with water, and the cla-tic cell wall with which it is in contact is also 
saturated. From tin- cell wall tin- water evaporates into the intercellular 
spaces, but the water is given up slowly through the protoplasmic mem- 
brane so that the water vapor cannot be given off as rapidly from the cell 
walls as it could if the protoplasm were dead. The living protoplasmic 



TRANSPIRA '/VOX. 



39 



membrane then which is only slowly permeable to the water of the cell-sap 
i> here a very important factor in checking the too rapid Loss of water from 
the leaves. 

By an examination of our leaf section we see that the intercellular spaces 
are all connected, and that the stomata, where they occur, open also into 
intercellular spaces. There is here an opportunity for the water vapor in 
the intercellular spaces to escape when the stomata are open. 

84. Action of the stomata. — Besides permitting the escape of the water 
vapor when the stomata are open the}* serve a V( ry important office in regu- 
lating the amount of transpiration. During normal transpiration the stomata 
remain open, that is, when the amount of transpiration from the leaf is not 
in excess of the supply of water to the leaves. But when the transpiration 
from the leaves is in excess, as often happens, and the air becomes very dry, 
the stomata close and thus the rapid transpiration is checked. 

85. Transpiration may be in excess of root pressure. — If the supply of 
water from the roots was always equal to that transpired from the leaves 
during hot, dry days the leaves would not become flaccid and droop. But 
during the hot and dry part of the day it often happens that the trans- 
piration is in excess of the amount of water supplied the plant by root 
pressure. 

86. Negative pressure. — This is not only indicated by the drooping of 
the leaves, but may be determined in another way. If the shoot of such a 
plant be cut underneath mercury, or underneath a strong solution of eosin, it 
will be found that some of the mercury or eosin, as the 
case may be, will be forcibly drawn up into the stem 
toward the roots. This is seen on quickly splitting the 
cut end of the stem. When plants in the open cannot 
be obtained in this condition, one may take a plant 
like a balsam plant from the greenhouse, or some other 
potted plant, knock it out of the pot, free the roots from 
the soil and allow to partly wilt. The stem may then 
be held under the eosin solution and cut. 

87. lifting power of transpiration. — Not only does 

transpiration go on quite independently of root pressure, 

as we have discovered from other experiments, but 

transpiration is capable of exerting a lifting power on 

the water in the plant. This may be demonstrated in 

the following way: Place the cut end of a leafy shoot in 

one end of a U tube and fit it water-tight. Partly Flg ' 37 ' 

,,, n . riT-r.T -i • , -i ' Experiment to show 

till this arm of the U tube with water, and add mercury lifting power of trans- 

to the other arm until it stands at a level in the two P iratlon - 

arms as in fig. 37. In a short time we note that the mercury is rising j n 

the tube. 




4Q 



PHYSIOLOGY. 



88. Root pressure may exceed transpiration. — If we cover small actively 
growing plants, such as the pea, corn, wheat, bean, etc., with a bell jar, and 
place in the sunlight where the temperature is suitable for growth, in a few 
hours, if conditions are favorable, we will see that there are drops of water 
standing out on the margins of the leaves. These drops of 
water have exuded through the ordinary stomata, or in other 
cases what are called water stomata, through the influence of 
root pressure. The plant being 

covered by the glass jar, the air 

,.. Q soon becomes saturated with mois- 

Estimation of the amount of ture and transpiration is checked. 




transpiration. The tubes are 
filled with water, and as the 
water transpires from the leaf 
surface its movement in the tube 
from a to b can be measured. 
(After Mangin.) 



Root pressure still goes on, how- 
ever, and the result is shown in 
the exuding drops. Root pressure 
is here in excess of transpiration. 
This phenomenon is often to be observed during the summer season in the case 
of low-crowing plants. During the bright warm day transpiration equals, 
or may be in excess of, root pressure, and the leaves are consequently 
flaccid. As nightfall comes 
on the air becomes more 
moist, and the conditions 
of light are such also that 
transpiration is lessened. 
Root pressure, however, is 
still active because the soil 
is still warm. In these cases 
drops of water may be seen 
exuding from the margins ot 
the leaves due to the excess 
of root pressure over trans- 
piration. Were it not for 
this provision for the escape 
of the excess of water raised 
by root pressure, serious in- 
jury by lesions, as a result 
of the great pressure, might 
result. The plant is thus to 
some extent a self-regulatory 
piece of apparatus so far as Fig. 39. 

root pressure and transpira- Guttation of tomato plants after connecting the stems by 
tion are concerned. means ol rubber tubes with the hyd,ant - 

89. Injuries caused by excessive root pressure. — Some varieties of to- 
matoes when grown in poorly Lighted and poorly ventilated greenhouses suffer 




TRA NSPIRA TION. 4 l 

serious injury through lesions of the tissues. This is brought about by the 
cells at certain parts becoming charged so full with water through the activity 

of root pressure and lessened transpiration, assisted also probably by an ac- 
cumulation of certain acids in the cell-sap which cannot be got rid of by 
transpiration. Under these conditions some of the cells here swell out 
forming extensive cushions, and the cell walls become so weakened that they 
burst. It is possible to imitate the excess of root pressure in the case of some 
plants by connecting the stems with a system of water pressure, when very 
quickly the drops of water will begin to exude from the margins of the leaves. 

90. It should be stated that in reality there is no difference between trans- 
piration and evaporation, if we bear in mind that evaporation takes place 
more slowly from living plants than from dead ones, or from an equal surface 
of water. 

91. The escape of water vapor is not the only function of the stomata. 
The exchange of gases takes place through them as we shall later see. A 
large number of experiments show that normally the stomata are open when 
the leaves are turgid. But when plants lose excessive quantities of water on 
dry and hot days, so that the leaves become flaccid, the guard cells automat- 
ically close the stomata to check the escape of water vapor. Some water 
escapes through the epidermis of many plants, though the cuticularized mem- 
brane of the epidermis largely prevents evaporation. In arid regions plants 
are usually provided with an epidermis of several layers of cells to more 
securely prevent evaporation there. In such cases the guard cells are often 
protected by being sunk deeply in the epidermal layer. 

92. Demonstration of stomates and intercellular air spaces.— A good 
demonstration of the presence of stomates in leaves, as well as the presence 
and intercommunication of the intercellular spaces, can be made by blowing 
into the cut end of the petiole of the leaf of a calla lily, the lamina being 
immersed in water. The air is forced out through the stomata and rises as 
bubbles to the surface of the water. At the close of the experiment some of 
the air bubbles will still be in contact with the leaf surface at the opening of the 
stomata. The pressure of the water gradually forces this back into the leaf. 
Other plants will answer for the experiment, but some are more suitable than 
others. 



CHAPTER VII. 

PATH OF MOVEMENT OF LIQUIDS IN PLANTS. 

93. In our study of root pressure and transpiration we have 
seen that large quantities of water or solutions move upward 
through the stems of plants. We are now led to inquire 
through what part of the stems the liquid passes in this upward 
movement, or in other words, what is the path of the "sap" as 
it rises in the stem. This we can readily see by the following 
trial. 

94. Place the cut ends of leafy shoots in a solution of some 
of the red dyes. — We may cut off leafy shoots of various plants 
and insert the cut ends in a vessel of water to which have been 
added a few crystals of the dye known as fuchsin to make a deep 
red color (other red dyes may be used, but this one is especially 
good). If the study is made during the summer, the "touch- 
me-not" (impatiens) will be found a very useful plant, or the 
garden -balsam, which may also be had in the winter from con- 
servatories. Almost any plant will do, however, but we should 
also select one like the corn plant (zea mays) if in the summer, 
or the petioles of a plant like caladium, which can be obtained 
from the conservatory. If seedlings of the castor-oil bean are at 
hand we may cut off some shoots which are 8-10 inches high, 
and place them in the solution also. 

95. These solutions color the tracts in the stem and leaves 
through which they flow. — After a few hours in the case of the 
impatiens, or the more tender plants, we can see through che 
stem that certain tracts are colored red by the solution, and 
after 12 to 24 hours there may be seen a red coloration of the 

42 



PATH OF MOVEMENT. 



43 



leaves of some of the plants used. After the shoots have been 
standing in the solution for a few hours, if we cut them at 
various places we will note that there are several points in the 
section where the tissues are colored red. In the impatiens 
perhaps from four to five, in the sunflower a larger number. In 
these plants the colored areas on a cross section of the stem are 
situated in a concentric ring which separates more or less com- 
pletely an outer ring of the stem from the central portion. If 
we now split portions of the stem lengthwise we see that these 
colored areas continue throughout the length of the stem, in some 
cases even up to the leaves and into them. 

96. If we cut across the stem of a corn plant which has been 
in the solution, we see that instead of the colored areas being in 
a concentric ring they are irregularly scattered, and on splitting 




Fig. 40. 
Broken corn stalk, showing fibro-vascular bundles. 

the stem we see here also that these colored areas extend for long 
distances through the stem. If we take a corn stem which is 
mature, or an old and dead one, cut around through the outer 
hard tissues, and then break the stem at this point, from the 
softer tissue long strings of tissue will pull out as shown in fig. 
40. These strings of denser tissue correspond to the areas 
which are colored by the dye. They are in the form of minute 
bundles, and are called vascular bundles. 



44 



PHYSIOLOGY. 



97. We thus see that instead of the liquids passing through 
the entire stem they are confined to definite courses. Now that 
we have discovered the path of the upward movement of water 
in the stem, we are curious to see what the structure of these 
definite portions of the stem is. 

98. Structure of the fibro-vascular bundles. — We should now make quite 
thin cross sections, either free hand and mount in water for microscopic 
examination, or they may be made with a microtome and mounted in Canada 
balsam, and in this condition will answer for future stud}'. To illustrate the 
structure of the bundk- in one type we may take the stem of the castor-oil 
bran. ( )n examining these cross sections we see that there are groups of 
cells which are denser than the ground tissue. These groups correspond to 
the colored areas in tin- former experiments, and are the vascular bundles 




Fig. 41. 

\vliin portion ol bundle Cambium portion ol bundle. Bast portion of bundle 

Set lion <>t vascular bundle <>t sunflower stem. 

Cut across. These groups are somewhat oval in outline, with the pointed 

end directed toward the center of the stem. If we look at the section as a 
whole we will see that there i-> a narrow continuous ring* of -mall cells 

!: This ring and the bundles separate the stem into two regions, an outer 
one composed <>l large cells with thin walls, known as the cortical cells, or 
collectively the cortex. The inner portion, corresponding to what is called 
the pith, i- made up «»l the same kind oi cells and i- called the medulla, or 
pith. When the cells of tin- cortex, as well a- of the pith, remain thin walled 
the tissue i- called parenchyma. Parenchyma belongs to the group oi 
tissues i ailed fund a mental. 



PATH OF MOVEMENT. 45 

situated at the same distance from the center of the stem as the middle part 
of the bundles, and that it divides the bundles into two groups of cells. 

99. Woody portion of the bundle. -In that portion of tin- bundle on the 
inside of the ring, i.e.. toward the ••pith." we note large, circular, or angu- 
lar cavities. The walls of these cell- arc quite thick and wood\'. Thej are 
therefore called wood cell-, and because they are continuous with cells above 
and below them in the stem in such a way that long tubes are formed, they 
are called woody vessels. Mixed in with these are smaller cells, some of 
which also have thick walls and are wood cells. Some of these cells may 
have thin walls. This is the case with all when they are young, and they 
are then classed with the fundamental tissue or soft tissue (parenchyma). 
Thi> part of the- bundle, since it contain- woody vessels and fibres, is the 
wood portion of the bundle, or technically the xylem, 

100 Bast portion of the bundle. — If our section is through a part of the 
stem which is not too young, the tissues of the outer part of the bundle will 
show either one or several groups of cells which have white and shiny walls, 
that are thickened as much or more than those of the wood vessels. These 
cells are bast cells, and for this reason this part of the bundle is the bast por- 
tion, or the phloem. Intermingled with these, cells may often be found which 
have thin walls, unless the bundle is very old. Nearer the center of the 
bundle and still within the bast portion are cells with thin walls, angular and 
irregularly arranged. This is the softer portion of the bast, and some of 
the>e cells are what are called sieve tubes, which can be better seen and 
studied in a longitudinal section of the stem. 

101. Cambium region of the bundle. — Extending across the center of the 
bundle are several rows of small cells, the smallest of the bundle, and we can 
see that they are more regularly arranged, usually in quite regular rows, 
like bricks piled upon one another. These cells have thinner walls than any 
others of the bundle, and they usually take a deeper stain when treated 
with a solution of some of the dyes. This is because they are younger, and 
are therefore richer in protoplasmic contents, This zone of young cells 
across the bundle is the cambium. Its cells grow and divide, and thus increase 
the size of the bundle. By this increase in the number of the cells of the 
cambium layer, the outermost cells on either side are continually passing 
over into the phloem, on the one hand, and into the wood portion of the 
bundle, on the other hand. 

102. Longitudinal section of the bundle. — If we make thin longisectionsof 
the vascular bundle of the castor-oil seedling (or other dicotyledon) so that we 
have thin ones running through a bundle radially, as shown in fig. 42, we 
can see the structure oi these part- of the bundle in side view. We see here 
that the form of the cells is very different from what is presented in a cross 
section of the same. The walls of the various duet- have peculiar markings 
on them. These markings are caused by the walls being thicker in -ohm- 



46 



PHYSIOLOGY. 



places than in others, and this thickening takes place so regularly in some 
instances as to form regular spiral thickenings. Others have the thickenings 





Fig. 42. 
Longitudinal section of vascular bundle of sunflower stem ; spiral, scalariform and pitted 
vessels at left ; next are wood fibers with oblique cross walls ; in middle are cambium cells 
with straight cross walls, next two sieve tubes, then phloem or bast cells. 

in the form of the rounds of a ladder, while still others have pitted walls or the 
thickenings are in the form of rings. 

103. Vessels or ducts. — One way in which the cells in side view differ 
greatly from an end view, in a cross section in the bundle, is that they are 
much longer in the direction of the axis of the stem. The cells have become 
elongated greatly. If we search for the place where two of these large cells 
with spiral, or ladder-like, markings meet end to end, we will see that the 
w;ill which formerly separated the cells has nearly or quite disappeared. In 
other words the two cells have now an open communication at the ends. 
This is so for long distances in the stem, so that long columns of these large 
cells form tubes or vessels through which the water rises in the steins of 
plants. 

104. In the bast portion of the bundle we detect the cells of tin- bast fibers 
by their thick walls. They are verj much elongated and the ends taper out to 
thin points so that they overlap. In this way they serve to strengthen the stem. 

105. Sieve tubes. -Lying near the bast cells, usually toward the cambium, 
aii- elongated cells standing end to end, with delicate markings on their cross 
walls which appear like finely punctured plates or sieves. The protoplasm 
in -luh cells is usually quite distinct, and sometimes contracted away from 
the side walls, but attached t<> the cross \\ ills, and this aids in the detection 
ot tli<- sieve tube (fig. \ 2. ) The granular appearance w hi< h these plates pre- 
sent is caused b) minute perforations through the wall v <» that there Is .1 com- 
munication between the cells. The tubes thus formed are therefore called 
sieve tubes and thei extend for lony distances through the tube so that there 



PATH OF MOVEMENT. 



47 



is communication throughout the entire length of the stem. (The function of 
the sieve tubes is supposed to be that for the downward transportation of sub- 
stances elaborated in the leaves.) 

106. If we section in like manner the stem of the sunflower we shall see simi- 
lar bundles, but the number is greater than eight. In the garden balsam the 
number is from four to six in an ordinary stem 3-4/;/;// diameter. Here we 
can see quite well the origin of the vascular bundle. Between the larger 
bundles we can see especially in free-hand sections of stems through which 
a colored solution has been lifted by transpiration, as in our former experi- 
ments, small groups of the minute cells in the cambial ring which are colored. 
These groups of cells which form strands running through the stem are pro- 
cambium strands. The cells divide and increase just like the cambium cells, 
and the older ones thrown off on either side change, those toward the center 
of the stem to wood vessels and fibers, and those on the outer side to bast 
cells and sieve tubes. 

107. Fibrovascular bundles in the Indian corn. — We should now make 
a thin transection of a portion of the center of the stem of Indian corn, in 
order to compare the structure of the 
bundle with that of the plants which we 
have just examined. In fig. 43 is repre- 
sented a fibrovascular bundle of the stem 
of the Indian corn. The large cells are 
those of the spiral and reticulated and 
annular vessels. This is the woody por- 
tion of the bundle or xylem, Opposite 
this is the bast portion or phloem, marked 
by the lighter colored tissue at i. The 
larger of these cells are the sieve tubes, 
and intermingled with them are smaller 
cells with thin wails. Surrounding the 
entire bundle are small cells with thick 
walls. These are elongated and the taper- Fig 43 

ing ends overlap. They are thus slender Transection of fibrovascular bundle of 
and long and form fibers. In such a ^^^M-S^^T^ 
bundle all of the cambium has passed vessel; r, annular vessel: /, air cavity 

formed by breaking apart of the cells ; z, 
over into permanent tissue and is said to so ft bast, a form of sieve tissue ; /, thin- 
1 , 1 walled parenchyma. (Sachs.; 

108. Rise of water in the vessels. — During the movement of the water or 
nutrient solutions upward in the stem the vessels of the wood portion of the 
bundle in certain plants are nearly or quite filled, if root pressure is active 
and transpiration is not very rapid. If, however, on dry days transpiration 
is in excess of root pressure, as often happens, the vessels are not tilled with 
the water, but are partly filled with certain gases because the air or other 




4 8 



PHYSIOLOGY. 



Epiderma 

system. 



gases in the plant become rarefied as a result of the excessive loss of water. 
There are then successive rows of air or gas bubbles in the vessels separated 
by films of water which also line the walls of the vessels. The condition of 
the vessel is much like that of a glass tube through which one might pass the 
•• froth " which is formed on the surfa :e of soapy water. This forms a chain 
of bubbles in the vessels. This chain has been called Jamin's chain because 
of the discoverer* 

109 Why water or food solutions can be raised by the plant to the height 
attained by some trees has never been satisfactorily explained. There are 
several theories propounded which cannot be discussed here. It is probably 
a very complex process. Root pressure and transpiration both play a part, 
or at least can be shown, as we have seen, to be capable of lifting water to a 
considerable height. In addition to this, the walls of the vessels absorb water 
by diffusion, and in the small vessels capillarity comes also into play, as 
well as osmosis. 

110. Synopsis of tissues. 
Epidermis. 

Simple hairs. 
Many-celled hairs. 
Trichomes Branched hairs, often stellate. 
liairs). Clustered, tutted hairs. 

( rlandular hairs. 
Root hairs. 
( ruard cells of stomates. 
Spiral vessels. 
Pitted vessels. 
Scalariform vessels. 
Annular vessels. 
Wood fibers. 

Wood parenchyma. 

( 'anibium ( fascicular). 
I Sieve tubes. 

Phloem. Bas1 fibers. 

i Bast parenc In ma. 
Cork. 
Paren< hyma. 

< .i i Mind tissue. 

Intel fascicula i i ambium. 

Me< lulla i \ ra) s. 
Bundle sheath. 

Schlerenchyma (thick walled cells, in nuts, etc)! Colleri- 
chyma (thick angled cells, under epidermis <>i succulent 



Xylem. 



Fibrovascular i 
system. 



Fundamental 
tern. 



CHAPTER VIII. 



DIFFUSION OF GASES. 



111. Gas given off by green plants in the sunlight. — Let 

us take some green alga, like spirogyra, which is in a fresh con- 
dition, and place one lot in a beaker or tall glass vessel of water 
and set this in the direct sunlight or in a well lighted place. At 
the same time cover a similar vessel 
with spirogyra with black cloth so that 
it will be in the dark, or at least in 
very weak light. 

112. In a short time we note that in 
the first vessel small bubbles of gas are 
accumulating on the surface of the 
threads of the spirogyra, and now and 
then some free themselves and rise to 
the surface of the water. Where there 
is quite a tangle of the threads the gas 
is apt to become caught and held back 
in larger bubbles, which on agitation of 
the vessel are freed. 

If We nOW examine the Second Vessel Oxygen gas given off by spirogyra. 

we see that there are no bubbles, or only a very few of them. 
We are led to believe then that sunlight has had something to 
do with the setting free of this gas from the plant. 

113. We may now take another alga like vaucheria and per- 
form the experiment in the same way, or to save time the 
two may be set up at once. In fact if we take any of the green 

49 





50 PHYSIO log v. 

algae and treat them as described above gas will be given off in a 
similar manner. 

114. We may now take one of the higher green plants, an 
aquatic plant like elodea, callitriche, etc. Place the plant in 
► the water with the cut end of the stem uppermost, 
but still immersed, the plant being weighted down 
by a glass rod or other suitable object. If we 
place the vessel of water containing these leafy 
stems in the bright sunlight, in a short time bub- 
bles of gas will pass off quite rapidly from the cut 
end of the stem. If in the same vessel we 
place another stem, from which the leaves 
have been cut, the number of bubbles of gas 
td iu/ lg 'r 45 ' given off will be very few. This indicates that 

Bubbles of oxygen gas ° J 

given off from elodea in a i ar g e part of the gas is furnished by the 

presence of sunlight. ° r ° J 

<° els -> leaves. 

115. Another vessel fitted up in the same way should be placed in the 
dark or shaded by covering with a box or black cloth. It will be seen here, 
as in the case of spirogyra, that very few or no bubbles of gas will be set 
free. Sunlight here also is necessary for the rapid escape of the gas. 

116. We may easily compare the rapidity with which light of varying 
intensity effects the setting free of this gas. After cutting the end of the stem 
let us plunge the cut surface several times in melted paraffine, or spread 
over the cut surface a coat of varnish. Then prick with a needle a small 
hole through the paraffine or varnish. Immerse the plant in water and 
place in sunlight as before. The gas now comes from the puncture through 
the coating of the cut end, and the number of bubbles given off during a 
given period can be ascertained by counting. If we duplicate this experi- 
ment by placing one plant in weak light or diffused sunlight, and another in 
the shade, we can easily compare the rapidity of the escape of the gas under 
the different conditions, which represent varying intensities of light. We 
see then that not only is sunlight necessary for the setting free of this gas, but 
that in diffused li^ht or in the shade the activity of the plant in this respect 
is less than in direct sunlight. 

117. What this gas is. — If we take quite a quantity of the 
plants of elodea and place them under an inverted funnel 
which is immersed in water, the gas will be given off in quite 
large quantities and will rise into the narrow exitot the funnel. 



DIFFUSION OF GASES. 



5< 



The funnel should be one with a short tube, or the vessel one 
which is quite deep so that a small test tube which is filled with 
water may in this condition be inverted over the 
opening of the funnel tube. With this arrange- 
ment of the experiment the gas will rise in the 
inverted test tube, slowly displace a portion of 
the water, and become collected in a sufficient 
quantity to afford us a test. When a consider- 
able quantity has accumulated in the test tube, we 
may close the end of the tube in the water with 
the thumb, lift it from the water and invert. . Flg * 46 - 

Apparatus for col- 

The gas will rise against the thumb. A dry Acting quantity of 

00 J oxygen from elodea. 

soft pine splinter should be then lighted, and ( D etmer.) 
after it has burned a short time, extinguish the flame by blowing 
upon it, when the still burning end of the splinter should be 
brought to the mouth of the tube as the thumb is quickly moved 
to one side. The glowing of the splinter shows that the gas is 




118. Oxygen given off by green land plants also. — If we should extend 
our experiments to land plants we would find that oxygen is given off by 
them under these conditions of light. Land plants, however, will not do 
this when they are immersed in water, but it is necessary to set up rather 
complicated apparatus and to make analyses of the gases at the beginning 
and at the close of the experiments. This has been done, however, in a suffi- 
ciently large number of cases so that we know that all green plants in the 
sunlight, if temperature and other conditions are favorable, give off oxygen. 

119. Absorption of carbon dioxide. — We have next to inquire 
where the oxygen comes from which is given off by green plants 
when exposed to the sunlight, and also to learn something more 
of the conditions necessary for the process. We know that 
water which has been for some time exposed to the air and soil, 
and has been agitated, like running water of streams, or the 
water of springs, has mixed with it a considerable quantity of 
oxygen and carbon dioxide. 

120. If we boil spring water or hydrant water which comes 
from a stream containing oxygen and carbon dioxide, for about 20 



52 PHYSIOLOGY. 

minutes, these gases are driven off. We should set this aside 
where it will not be agitated, until it has cooled sufficiently to 
receive plants without injury. Let us now place some spirogyra 
or vaucheria, and elodea, or other green water plant, in this 
boiled water and set the vessel in the bright sunlight under the 
same conditions which were employed in the experiments for the 
evolution of oxygen. No oxygen is given off. 

121. Can it be that this is because the oxygen was driven 
from the water in boiling ? We will see. Let us take the vessel 
containing the water, or some other boiled water, and agitate it 
so that the air will be thoroughly mixed with it. In this way 
oxygen is again mixed with the water. Now place the plant 
again in the water, set in the sunlight, and in several minutes 
observe the result. No oxygen is given off. There must be 
then some other requisite for the evolution of the oxygen. 

122. The gases are interchanged in the plants. — We will 
now introduce carbon dioxide again in the water. This can be 
done by blowing into the water through a glass tube in such a 
manner as to violently agitate the water for some time, when the 
carbon dioxide from the "breath" will become mixed with the 
water. Now if we place the plant in the water and set the vessel 
in the sunlight, in a few minutes the oxygen is given off rapidly. 

123. A chemical change of the gas takes place within the 
plant cell. — This leads us to believe then that C0 2 is in some 
way necessary for the plant in this process. Since oxygen is 
given off while carbon dioxide, a different gas, is necessary, it 
would seem that a chemical change takes place in the gases 
within the plant. Since the process takes place in such simple 
plants as spirogyra as well as in the more bulky and higher 
plants, it appears that the changes go on within the cell, in fact 
within the protoplasm. 

124. Gases as well as water can diffuse through the proto- 
plasmic membrane. — Carbon dioxide then is absorbed by the 
plant while oxygen is given off. We see therefore that gases as 
well as water can diffuse through the protoplasmic membrane of 
plants under certain conditions. 



DIFFUSION OF GASES. 53 

125. Note. If we kill the plant, for example, by placing it fora shorl time in 
nearly boiling water, oxygen will not be given off when the plant is placed in 
the sunlight in water. In other words the plant must be alive. Farther, if 
we introduce C0 2 in the water by blowing into it and have not introduced 
oxygen, oxygen will not be evolved. Not only must the plant be aliv< . it 
must have access to oxygen, which we will see later is very essential to the 
continuance of one of the important life processes. 



CHAPTER IX. 



RESPI RATION 



126. One of the life processes in plants which is extremely 
interesting, and which is exactly the same as one of the life pro- 
cesses of animals, is easily demonstrated in several ways. 

127. Oxygen from the air consumed during germination of 
seeds.— Let us take a half pint or a pint of peas, tie them in a 

bag or loose cloth, soak them in warm water 
for 10 or 12 hours, or in cool water for about 
24 hours. Drain off the surplus water and lower 
the cloth with the peas in a tall glass cylinder 
which holds 1 to 2 liters. This should be 
covered with a glass plate after vaseline has 
been smeared on the edges of the cylinder to 
make the vessel air tight. Set aside in a warm 
room for about 12 hours. Now lower a lighted 
taper or short candle into the vessel after having 




carefully removed the cover. The flame is 
extinguished. This indicates that there is no 



47. 

Tesl f< tr pre en< e "t 
carbon dioxide in vessel oxygen in the vessel. 
with germinating peas. - 

(Sachs.) 128. Carbon dioxide given off during ger- 

mination. Now lei us lower a small vessel containing lime water 
into it. Very soon, almost immediatel) , there is formed on the 
surface of the lime water a film. The film formed under these 
conditions is known to be carbonate of lime, which is formed by 

the union of carbon dioxide in the vessel with the lime in the 

watei . ( Note. Where there are a number of students and large 
vessels are not ;it hand, bottles of a pint capacity and a smaller 

number oi peas will answer. ) 

54 



RESPIRA TION. 



55 



129. If we now take some of the lime water and blow our 
"breath" upon it the same film will be formed. The carbon 
dioxide which we exhale unites with the lime in the water, and 
forms carbonate of lime, just as in the case of the peas. In the 
case of animals the process by which oxygen is taken into the 
body and carbon dioxide is given off is respiration. The process 
in plants which we are now studying is the same, and also is 
respiration. The oxygen in the vessel was used up in the proc- 
ess, and carbon dioxide was given off. (It will be seen that 
this process is exactly the opposite of that which takes place in 
carbon conversion. ) 

130. Respiration is necessary for growth. — After we have performed this 
experiment, if the vessel has not been open too long so that oxygen has en- 
tered, we may use the vessel for another experiment, or set up a new one to 
be used in the course of 12 to 24 hours, after all the oxygen has been con- 
sumed. Place some folded damp filter paper on the germinating peas in the 
jar. Upon this place one-half dozen peas which have just been germinated, 
and in which the roots are about 20-25 mm long. The vessel should be cov- 
ered tightly again and set aside in a warm room. 
A second jar with water in the bottom instead 
of the germinating peas should be set up as a 
check. Damp folded filter paper should be sup- 
ported above the water, and on this should be 
placed one -half dozen peas with roots of the 
same length as those in the jar containing carbon 
dioxide. 

131. In 24 hours examine and note how much Fig. 48. 

growth has taken place. It will be seen that the p f a seedlings ; the one 

at the left had no oxygen 
roots have elongated but very little or none in the and little growth took 

first jar, while in the second one we see that the in^xvgen and CTowthwas 

roots have elongated considerably, if the experi- evid ent. 

ment has been carried on carefully. Therefore 

in an atmosphere devoid of oxygen very little growth will take place, which 

shows that normal respiration with access of oxygen is necessary for growth. 

132. Energy set free during respiration. — From what we have learned of 
the exchange of gases during respiration we infer that the plant loses carbon 
during this process. If the process of respiration is of any benefit to the 
plant, there must be some gain in some direction to compensate the plant for 
the loss of carbon which takes place. 

It can be shown by an experiment that during respiration there is a 
slight elevation of the temperature in the plant tissues. The plant then 






56 PHYSICLOG Y. 

gains some heat during respiration. We have also seen in the attempt to 
grow seedlings in the absence of oxygen that very little growth takes place. 
But when oxygen is admitted growth takes place rapidly. The process of 
respiration, then, also sets free energy which is manifested in one direction, 
by growth. 

133. Respiration in a leafy plant. — We may take a potted plant which 
has a well-developed leaf surface and place it under a tightly fitting bell jar. 

Under the bell jar there also should be placed a 
small vessel containing lime water. A similar ap- 
paratus should be set up, but with no plant, to serve 
as a check. The experiment must be set up in a 
room which is not frequented by persons, or the 
carbon dioxide in the room from respiration will 
vitiate the experiment. The bell jar containing the 
plant should be covered with a black cloth to pre- 
vent carbon assimilation. In the course of ten or 

i-i 49 - r twelve hours, if everything has worked properly, the 
lest for liberation of car- . . . 

bon dioxide from leafy plant lime water under the jar with the plant will show the 

water in smaller vessel. nmi °f carbonate of lime, while the other one will 

(Sachs.) show none. Respiration, therefore, takes place in 

a leafy plant as well as in germinating seeds. 

134. Respiration in fungi. — If several large actively growing mushrooms 
are accessible, place them in a tall glass jar as described for determining 
respiration in germinating peas. In the course of twelve hours test with the 
lighted taper and the lime water. Respiration takes place in fungi as well 
as in green plants. 

135. Respiration in plants in general. — Respiration is general in all 
plants, though not universal. There are some exceptions in the lower plants, 
notably in certain of the bacteria, which can only grow and thrive in the ab- 
sence of oxygen. 

136. Respiration a breaking-down process. — We have seen that in res- 
piration the plant absorbs oxygen and gives off carbon dioxide. W r e should 
endeavor to note some of the effects of respiration on the plant. Let us 
take, say, two dozen dry peas, weigh them, soak for 12-24 hours in water, 
and, in the folds of a cloth kept moist by covering with wet paper or sphag- 
num, germinate them. When well germinated and before the green color 
appears dry well in the sun. or with artificial heat, being careful not to burn 
or scorch them. The aim should In- to get them about as dry as the seed 
wrrc before germination. Now weigh. The germinated seeds weigh less 
than the dry peas. There lias then been a loss of plant substance during 
respiration. 

137. Detailed result of the above experiment to show that respiration is 
necessary for growth. The experiment was . tarted at 9.30 a.m. on July 



REST IRA TION. 



57 



8. and the roots measured 20-25;///;/. ^ 3 P - M - on the following day, 
29 hours after the experiment was started, the roots were examined. Those 
in the CO... gas had not grown perceptibly, while those in the jar containing 
air had increased in length 10-20/;//;/. In fig. 48 are represented two of the 
peas, drawn at the close of the experiment, a represents the one from the 
CO a jar which had the longest root, b represents one of the longer ones from 
the jar with air. Here we have also a good comparison with the peas 
grown in the mercury tubes, since those in the tube which contained some 
air were checked in growth to a considerable extent, by the accumulation of 
carbon dioxide in the small space in the tube, ancTdld not represent a fair 
comparison of root growth in air and in CO^. 

138. Another way of performing the experiment. — If we wish we may 
use the following experiment instead of the simple one indicated above. Soak 
a handful of peas in water for 12-24 
hours, and germinate so that twelve 
with the radicles 20-25/;//// l° n S 
may be selected. Fill a test tube 
with mercury and carefully invert 
it in a vessel of mercury so that 
there will be no air in the upper end 
(there may be a small vacuum). 
Now nearly fill another tube and 
invert in the same way. In the 
latter there will be some air. Re- 
move the outer coats from the peas 
so that no air will be introduced in 
the tube filled with the mercury, 
and insert them one at a time under 
the edge of the tube beneath the 
mercury, six in each tube, having 
first measured the length of the 
radicles. Place in a warm room. 
In 24 hours measure the roots. 
Those in the air will have grown 
considerablv. while those in the 




Fig. 50- 
Experiment to show that growth takes place 
more rapidly in presence of oxygen than in ab- 
sence of oxygen. At the beginning of the experi- 
ment the two tubes in the vessel represent the 
condition at the beginning of the experiment. 
At the close the roots in the tube at the left were 
longer than those in the tube filled at the start 
other tube will have grown but with mercury. The tube outside of the vessel 
. . . represents the condition of things where the peas 

little or none. grew in absence of oxygen ; the carbon dioxide 

The apparatus to demonstrate given off has displaced a portion of the mercury. 

this was set up at 10 a.m. on July 
8. 1897. The tube filled with mercury was supported by a clamp, while 
the tube which was only partly filled was stable enough to support itself 
until by the accumulation of gas nearly all the mercury moved out. when 
it was weighted down. 



This also shows intramolecular respiration. 



58 PHYSIOLOGY. 

The twelve peas were selected so that six for each lot showed the same 
length of root, which varied from 15 to 25 mm long. Fig. 50 shows the 
apparatus just after the experiment was started. The peas in tube a (the 
right-hand tube) are nearly hidden by the mercury. 

At 2 r.M. the accumulation of gas had caused the lowering of the 
mercury in this tube so that the upper pea was entirely uncovered. At 4 
P.M. another pea was uncovered. By this time it was evident that the roots 
of the peas in tube b (left-hand one) were elongating, while no increase could 
be detected in the roots of the peas in a. At 6 p.m. three peas in a were 
uncovered. At 10 p.m. all six peas were uncovered. The roots of the peas 
in b were still longer than when noted at 4 P.M., but in a no elongation was 
perceptible at that time. At 9 a.m. on the following day the mercury had 
lowered so that it was nearly level with the mercury in the dish, while that 
in tube b was below the level of that in the dish. There was no perceptible 
elongation of the roots in a, while the roots in b measured about 5 mm 
longer than when the experiment was started. 

139. Intramolecular respiration. — The last experiment is also an excel- 
lent one to show what is called intramolecular respiration. In the tube filled 
with mercury so that when inverted there will be no air, it will be seen after 
24 hours that a gas has accumulated in the tube which has crowded out some 
of the mercury. With a wash bottle which has an exit tube properly curved, 
some water may be introduced in the tube. Then insert underneath a small 
stick of caustic potash. This will form a solution of potash and the gas will 
be partly or completely absorbed. This shows that the gas was carbon 
dioxide. This evolution of carbon dioxide by living plants when there is no 
access of oxygen is called intramolecular respiration. It occurs markedly in 
oily seeds and especially in the yeast plant. 



CHAPTER X. 

THE CARBON FOOD OF PLANTS. 

140. We came to the conclusion in a former chapter that 
some chemical change took place within the protoplasm of the 
green cells of plants during the absorption of carbon dioxide 
and the giving off of oxygen. We should examine some of the 
green parts of those plants used in the experiments, or if they are 
not at hand we should set up others in order to make this ex- 
amination. 

141. Starch formed as a result of carbon conversion. — We 
may take spirogyra which has been standing in water in the 
bright sunlight for several hours. A few of the threads should 
be placed in alcohol for a short time to kill the protoplasm. 
From the alcohol we transfer the threads to a solution of iodine 
in potassium iodide. We will find that at certain points in the 
chlorophyll band a bluish tinge, or color, is imparted to the ring 
or sphere which surrounds the pyrenoid. In our first study of 
the spirogyra cell we noted this sphere as being composed of 
numerous small grains of starch which surround the pyrenoid. 

142. Iodine used as a test for starch. — This color reaction 
which we have obtained in treating the threads with iodine is 
the well-known reaction, or test, for starch. We have demon- 
strated then that starch is present in spirogyra threads which 
have stood in the sunlight with free access to carbon dioxide. 

If we examine in the same way some threads which have stood in 
the dark for a day we will get no reaction for starch, or at best 
only a slight reaction. This gives us some evidence that a 
chemical change does take place during this process (absorption 

59 



60 PHYSIOLOGY. 

of C0 a and giving off of oxygen), and that starch is a product of 
that chemical change. 

143. Schimper's method of testing for the presence of starch. 

— Another convenient and quick method of testing for the pres- 
ence of starch is what is known as Schimper's method. A 
strong solution of chloral hydrate is made by taking 8 grams of 
chloral hydrate for every $cc of water. To this solution is 
added a little of an alcholic tincture of iodine. The threads of 
spirogyra may be placed directly in this solution, and in a few 
moments mounted in water on the glass slip and examined with 
the microscope. The reaction is strong and easily seen. 

144. We may test vaucheria which has been grown under like 
conditions in the same way. We find here also that the starch 
is present in the threads which have been exposed to the sun- 
light, while it is absent from those which have been for a suffi- 
ciently long time in the dark. 

145. We should also examine the leaves of elodea, or one of 
the higher green plants which has been for some time in the 
sunlight. We may use here Schimper's method by placing the 
leaves directly in the solution of chloral hydrate and iodine. 
The leaves arc made transparent by the chloral hydrate so that 
the starch reaction from the iodine is easily detected. 

146 [f we wish to use tin- potassium iodide <>! iodine tin- leaves should be 
first boiled lor a short time in water, then heated for some time in alcohol, or 
the alcohol changed several times. The green color is extracted slowly by 
this process, and will be hastened if the preparation i- placed in tin- sunlight. 
(If care is used the leaves ma} In- boiled in alcohol.) After the leaves are 
decolorized they should 1>' immersed in the potassium iodide of iodine. 

147. Green parts of plants form starch when exposed to 

light. Thus we find that in the case ^\ all the green plants we 

have examined, starch is presenl in the green cells of those which 

have been standing for some time in the sunlighl where the proc 

.a the absorption ol CO a and the giving oil ol oxygen can 

on, and that in 1 he case 1 >i plants grown in t he dark, or in 

leaves of plants which have stood for some tune in the dark, 

i,m h is absent. We reason froin this that stan h is the product 



CARBON FOOD OF PLANTS. 6l 

of the chemical change which takes place in the green cells 
under these conditions. Because C0 2 is absorbed during this 
process, and because of the chemical changes which take place 
in the formation of starch, by means of which the carbon is 
changed from its attraction in the molecule of carbon dioxide to 
its attraction in the molecule of starch, the process may be 
termed carbon conversion. 

This process has been termed carbon assimilation, but since it is not truly 
an assimilatory process, and because sunlight is necessary in the first step 
of the conversion, it has also been recently termed photosyntax, or photo- 
synthesis. These terms, however, seem inappropriate, since the synthetic 
part of the process is not known to be due to the action of light. In the 
presence of chlorophyll light reduces the carbon dioxide, while the synthetic 
part of the process may not be influenced by light. Since the process is 
similar to that which chemists call conversion, and since the carbon is the 
important food element derived from the air, for popular treatment the term 
carbon conversion seems more appropriate. 

148. Starch is formed only in the green parts of variegated 
leaves. — If we test for starch in variegated leaves like the leaf of 
a coleus plant, we shall have an interesting demonstration of the 
fact that the green parts of plants only form starch. We may 
take a leaf which is partly green and partly white, from a plant 
which has been standing for some time in bright light. Fig. 51 is 
from a photograph of such a leaf. We should first boil it in 
alcohol to remove the green color. Now immerse it in the 
potassium iodide of iodine solution for a short time. The parts 
which were formerly green are now dark blue or nearly black, 
showing the presence of starch in those portions of the leaf, 
while the white part of the leaf is still uncolored. This is well 
shown in fig. 52, which is from a photograph of another coleus 
leaf treated with the iodine solution. 

149. Translocation of starch. — It has been found that leaves of green 
plants grown in the sunlight contain starch when examined after being in the 
sunlight for several hours. But when the plants are left in the dark for a 
day or two the leaves contain no starch, or a much smaller amount. This sug- 
gests that starch after it has been formed may be transferred from the leaves, 
or from those areas of the leaves where it has been formed. 



62 



PHYSIOLOGY. 



150. To test this let us perform an experiment which is often made. We 
may take a plant such as a garden tropa?olum or a clover plant, or other land 




Fig. 51- 
Leaf of coleus showing green and white 
areas, before treatment with iodine. 



Fig. 52. 
Similar leaf treated with iodine, the starch re- 
action only showing where the leaf was green. 



plant m which it is easy to test for the presence of starch. Pin a piece of 
circular cork, which is smaller than the area of the leaf, on either side of the 

leaf, as in fig. 53. Place the 
plant where it will be in the 
sunlight. On the afternoon 
of the following day, if the sun 
has been shining, we may 
remove the corks and test for 
starch, using the entire leaf, 
by Schimper's method. Or 
^^ ^^Eir*^ the method described in 146 

I<1R - 53, , M g- 54- may be employed. The part 

Leaf of tropaeolum Leaf of tropaeolum treated - . , " 

with portion covered with iodine alter removal of covered by the cork Will not 
with corks to prevent cork, to show that starch is re- . , „ a/ , f ;„ + - ^.,,.,.k 

theformationotstareh. moved from the leaf during the give the reaction tol Starch, 
(After Detmer.j night. as shown by the absence of the 

bluish color, while the other parts of the leaf will show it. The starch 
which was in that part of the Km! the day before was dissolved and removed 




CARBON FOOD OF PLANTS. 63 

during the night, and then during the following day, the parts being cov- 
ered from the light, no starch was formed in them. 

151. Starch in other parts of plants than the leaves. — We 

may use the iodine test to search for starch in other parts of 
plants than the leaves. If we cut a potato tuber, scrape some of 
the cut surface into a pulp, and apply the iodine test, we obtain 
a beautiful and distinct reaction showing the presence of starch. 
Now we have learned that starch is only formed in the parts 
containing chlorophyll. We have also learned that the starch 
which has been formed in the leaves disappears from the leaf or 
is transferred from the leaf. We judge therefore that the starch 
which we have found in the tuber of the potato was formed first 
in the green leaves of the plant, as a result of carbon assimila- 
tion. From the leaves it is transferred in solution to the under- 
ground stems, and stored in the tubers. The starch is stored 
here by the plant to provide food for the growth of new plants 
from the tubers, which are thus much more vigorous than the 
plants would be if grown from the seed. 

152. The potato is only one example of a great many cases where starch 
is stored up as a reserve material by plants, but not always in the form of 
tubers. In the sweet potato and some other plants it is stored in the roots, 
certain ones of the roots becoming very much thickened; in the onion it is 
stored in certain leaves which form the onion bulb. 

153. Form of starch grains. — Where starch is stored as a reserve material 
it occurs in grains which usually have certain characters peculiar to the 
species of plant in which they are found. They vary in size in many 
different plants, and to some extent in form also. If we scrape some of the 
cut surface of the potato tuber into a pulp and mount a small quantity in 
water, or make a thin section for microscopic examination, we will find 
large starch grains of a beautiful structure. The grains are oval in 
form and more or less irregular in outline. But the striking peculiarity is 
the presence of what seem to be alternating dark and light lines in the starch 
grain. We note that the lines form irregular rings, which are smaller 
and smaller until we come to the small central spot termed the " hilum " of 
the starch grain. It is supposed that these apparent lines in the starch 
grain are caused by the starch substance being deposited in alternating dense 
and dilute layers, the dilute layers containing more water than the dense 
ones; others think that the successive layers from the hilum outward are 



64 PHYSIOLOGY. 

regularly of diminishing density, and that this gives the appearance of alter- 
nating lines. The starch formed by plants is one of the organic substances 
which are manufactured by plants, and it is the basis for the formation of 
other organic substances in the plant. Without carbon food green plants 
cannot make any appreciable increase of plant substance, though a consider- 
able increase in size of the plant may take place. 



CHAPTER XL 

CHLOROPHYLL AND THE FORMATION OF STARCH. 

154. In our experiments thus far in treating of the absorption 
of carbon dioxide and the evolution of oxygen, with the accom- 
panying formation of starch, we have used green plants. 

155. Fungi cannot form starch. — If we should extend our 
experiments to the fungi, which lack the green color so charac- 
teristic of the majority of plants, we should find that carbon con- 
version does not take place even though the plants are exposed 
to direct sunlight. These plants cannot then form starch, but 
obtain carbohydrates for food from other sources. 

156. Etiolated plants cannot convert carbon. — Moreover 
carbon assimilation is usually confined to the green plants, and 
if by any means one of the ordinary green plants loses its green 
color carbon conversion cannot take place in that plant, even 
when brought into the sunlight, until the green color has 
appeared under the influence of light. 

This may be very easily demonstrated by growing seedlings 
of the bean, squash, corn, pea, etc. (pine seedlings are green even 
when grown in the dark), in a dark room, or in a dark receiver 
of some kind which will shut out the rays of light. The room 
or receiver must be quite dark. As the seedlings are "coming 
up," and as long as they remain in the dark chamber, they will 
present some other color than green; usually they are somewhat 
yellowed. Such plants are said to be etiolated. If they are 
brought into the sunlight now for a few hours and then tested 
for the presence of starch the result will be negative. But if the 
plant is left in the light, in a few days the leaves begin to take 

65 



66 



PHYSIOLOGY. 



on a green color, and then we find that carbon conversion 
begins. 

157. Chlorophyll and chloroplasts. — The green substance in 
plants is then one of the important factors in this complicated 
process of forming starch. This green substance is chlorophyll, 
and it usually occurs in definite bodies, the chlorophyll bodies, 
or chloroplasts. 

The material for new growth of plants grown in the dark is derived from 
the seed. Plants grown in the dark consist largely of water and protoplasm, 
the walls being very thin. 

158. Form of the chlorophyll bodies. — Chlorophyll bodies 
vary in form in some different plants, especially in some of the 
lower plants. This we have already seen in the case of 
spirogyra, where the chlorophyll body is in the form of a very 
irregular band, which courses around the inner side of the cell 
wall in a spiral manner. In zygnema, which is related to 
spirogyra, the chlorophyll bodies are star-shaped. In the 
desmids the form varies greatly. In cedogonium, another of 
the thread-like algae, illustrated in fig. 95, the chlorophyll bodies 




Fig. 55- 

Section of ivy leaf, palisade cells above, loose parenchyma, with large intercellular spaces 
in center. Epidermal (ells on either edge, with no chlorophyll bodies. 

are more or less flattened oval disks. In vaucheria, too, a 
branched thread-like alga shown in fig, 106, the chlorophyll 
bodies are oval in outline. These two plants, oedogonium and 



CHLOROPHYLL; STARCH. 6j 

vaucheria, should be examined here if possible, in order to be- 
come familiar with their form, since they will be studied later 
under morphology (see chapters on oedogonium and vaucheria, 
for the occurrence and form of these plants). The form of the 
chlorophyll body found in oedogonium and vaucheria is that 
which is common to many of the green algae, and also occurs in 
the mosses, liverworts, ferns, and the higher plants. It is a 
more or less rounded, oval, flattened disk. 

159. Chlorophyll is a pigment which resides in the chloroplast. — That 
the chlorophyll is a coloring substance which resides in the chloroplastid, 

and does not form the body itself, can be demonstrated by dissolving out the 
chlorophyll when the framework of the chloroplastid is apparent. The 
green parts of plants which have been placed for some time in alcohol lose 
their green color. The alcohol at the same time becomes tinged with green. 
In sectioning such plant tissue we find that the chlorophyll bodies, or chloro- 
plastids as they are more properly called, are still intact, though the green 
color is absent. From this we know that chlorophyll is a substance distinct 
from that of the chloroplastid. 

160. Chlorophyll absorbs energy from sunlight for carbon conversion. — It 
has been found by analysis with the spectrum that chlorophyll absorbs cer- 
tain of the rays of the sunlight. The energy which is thus obtained from 
the sun, called kinetic energy, is supposed to act on the molecules of C0 2 and 
H 2 0. separating them into other molecules of C, II, and (). and that after a 
series of complicated chemical changes starch is formed by the union of mole- 
cules of carbon, oxygen, and hydrogen, the hydrogen and some of the oxygen 
at least coming from the water in the cells of the plant. In this process of 
the reduction of the C0 2 and the formation of starch there is a surplus of 
oxygen, which accounts for the giving off of oxygen during the process. 

161. Bays of light concerned in carbon conversion. — If a solution of 
chlorophyll be made, and light be passed through it. and this light be 
examined with the spectrum, there appear what are called absorption bands. 
These are dark bands which lie across certain portions of the spectrum. 
These bands lie in the red. orange, yellow, green, blue, and violet, but the 
bands are stronger in the red. which shows that chlorophyll absorbs more of 
the red rays of light than of the other rays. These are the rays of low 
refrangibility. The kinetic energy derived by the absorption of these rays 
of light is transferred into potential energy. That is, the molecule of CO.., is 
broken up. and then by a different combination of certain elements starch is 
formed.* 



* In the formation of starch during carbon conversion the separated mole- 
cules from tin- carbon dioxide a\\(\ water unite in such a way that carbon, 



68 PHYSIOLOGY. 

162. Starch grains formed in the chloroplasts. — During carbon conver- 
sion the starch formed is deposited generally in small grains within the green 
chloroplast in the leaf. We can see this easily by examining the leaves of 
some moss like funaria which has been in the light, or in the chloroplasts 
of the prothallia of ferns, etc. Starch grains may also be formed in the 
chloroplasts from starch which was formed in some other part of the plant, 
but which has passed in solution. Thus the functions of the chloroplast are 
twofold, that of the conversion of carbon and the formation of starch grains. 

163. In the translocation of starch when it becomes stored up in various 
parts of the plant, it passes from the state of solution, into starch grains in 
connection with plastids similar to the chloroplasts, but which are not green. 
The green ones are sometimes called chromoplasts, while the colorless one- 
are termed leucopljtsts. 

164. Carbon conversion in other than green plants. — While organic com- 
pounds are usually only formed by green plants, there are some exception^ 
Apparent exceptions are found in the blue-green algae like oscillatoria, 
nostoc, or in the brown and red sea weeds like fucus, rhabdonia, etc. These 
plants, however, possess chlorophyll, but it is disguised by another pigment or 
color. There are plants, however, which do not have chlorophyll and yet 
form organic substance with evolution of oxygen in the presence of light, as 
for example a purple bacterium, in which the purple coloring substance 
absorbs light, though the rays absorbed most energetically are not the red. 

165. Influence of light on the movement of chlorophyll bodies. — In fern 
p'othallia. — If we place fern prothallia in weak light for a few hours, and 
then examine them under the microscope, we find that the most of the chloro- 
phyll bodies in the cells are arranged along the inner surface of the 
horizontal wall. If now the same prothallia are placed in a brightly lighted 
place for a short time most of the chlorophyll bodies move so that they are 
arranged along the surfaces of the perpendicular walls, and instead of having 
the flattened surfaces exposed to the light as in the former case, the edges 
of the chlorophyll bodies are now turned toward the light. (See figs. 
56, 57.) The same phenomenon has been observed in many plants. Light 
then has an influence on chlorophyll bodies, to some extent determining their 
position. In weak light they are arranged so that the flattened surfaces are 
exposed to the incidence of the rays of light, SO that the chlorophyll will 
absorb as great an amount as possible of kinetic energy; but intense light is 



hydrogen, and oxygen are united into a molecule of starch. This result i> 
usually represented by the following equation: CO a + H 9 = CHyO-f O a . 
Then by polymerization 6(CH a O) = Coll,./),, =r grape sugar. Then 
C 6 HuOfl — H 9 = C e H 1 O ft ss starch. It is believed, however, that the 
process is much more complicated than tin's, and that several different com- 
pounds are formed before starch finally appear-. 



CHLOROPHYLL; STARCH. 



6 9 



stronger than necessary, and the chlorophyll bodies move so that their edges 
are exposed to the incidence of the rays. This movement of the chlorophyll 
bodies is different from that which takes place in some water plants like- 




Fig. 56, Fig. 57. 

Ceil exposed to weak diffused light show- Same cell exposed to strong light, showing 

ing chlorophyll bodies along the horizontal chlorophyll bodies have moved to perpen- 
walls. dicular walls. 

Figs. 56, 57. — Cell of prothallium of fern. 

elodea. The chlorophyll bodies in elodea are free in the protoplasm. The 
protoplasm in the cells of elodea streams around the inside of the cell wall 
much as it does in nitella and the chlorophyll bodies are carried along in the 
currents, while in nitella they are stationary. 



CHAPTER XII. 

NUTRITION AND MEMBERS OF THE PLANT BOCV. 



166. In connection with the study of the means for obtaining nutriment 
from the soil or water by the green plants it will be found convenient to 
observe carefully the various forms of the plant. Without going into detail 
here the suggestion is made that simple thread forms like spirogyra, cedogo- 
nium, and vaucheria; expanded masses of cells as are found in the thalloid 
liverworts, the duckweed, etc. , be compared with those liverworts, and with the 
mosses, where leaf-like expansions of a central axis have been differentiated, 
and how this differentiation, from the physiological standpoint, has been 
carried farther in the higher land plants. 

167. Nutrition of liverworts. — In many of the plants termed liverworts 
the vegetative part of the plant is a thin, flattened, more or less elongated 
green body known as a thallus. 

Riccia. — One of these, belonging to the genus riccia, is shown in fig. 
58. Its shape is somewhat like that of a minute ribbon which is forked at 

intervals in a dichotomous man- 
ner, the characteristic kind of 
branching found in these thalloid 
liverworts. This riccia (known 
as R. lutescens) occurs on damp 
soil; long, slender, hair-like 
processes grow out from the 
rider surface of the thallus, 
which resemble root hairs and 
serve the same purpose in the 
processes of nutrition. Another 
species of riccia (R. crvstallina) 
is shown in fig. 171. This plant 
is quite circular in outline and 
occurs on muddy flats. Some 
Thallus of riccia lute 1 specieg |1((;U nn the water. 

168. Marchantia.— -One of the larger and coarser liverworts 

is figured at 59. This is a very common liverwort, growing in 

70 




Fig. 5 8. 
[>t ri< cia Lutescens. 



NUTRITION; MEMBERS PLANT BODY. 



71 



very damp and muddy places and also along the margins of 
streams, on the mud or upon the surfaces of rocks which are 
bathed with the water. This is known as Marchantia polymorpha. 
If we examine the under surface of the marchantia we see 
numerous hair-like processes which attach the plant to the soil. 
Under the microscope we see that some of these are exactly like 
the root hairs of the seedlings which we have been studying, 
and they here serve the same purpose. Since, however, there are 
no roots on the marchantia plant, these hair-like outgrowths are 




Fig- 59- 
Marchantia plant with cupules and gemmas ; rhizoids below. 

usually termed here rhizoids. In marchantia they are of two 
kinds, one kind the simple ones with smooth walls, and the 
other kind in which the inner surfaces of the walls are roughened 
by processes which extend inward in the form of irregular tooth- 
like points. Besides the hairs on the under side of the thallus 
we note especially near the growing end that there are two rows 
of leaf-like scales, those at the end of the thallus curving up 
over the growing end, and thus serve to protect the delicate 
tissues at the growing point. 



72 



PHYSIOLOGY. 



169. Frullania. — In fig. 60 is shown another liverwort, 
which differs greatly in form from the ones we have just been 
studying in that there is a well-defined axis with 
lateral leaf- like outgrowths. Such liverworts 
are called foliose liverworts. Besides these two 
quite prominent rows of leaves there is a third 
row of poorly developed leaves on the under 
surface. Also from the under surface of the axis 

we see here 
and there 
slender out- 
growths, the 
r h i z o i d s, 
through 
which much 
Fig - 62 \ of the liquid 

Under side 

showing forked nutriment is 

under row of 

leaves and lobes absorbed. 

of lateral leaves. 






Fig. 60. 
Portion of plant of 
Frullania, a foliose 
liverwort. 



Fig. 61. 
Portion of same 
more highly magni- 
fied, showing over- 
lapping leaves. 



170. Nutrition of the mosses. — Among the mosses which 
are usually common in moist and shaded situations, examples 
are abundant which are suitable for the study of the organs of 
absorption. If we take for example a plant of Mnium (M. affine) 
which is illustrated in fig. 64, we note that it consists of a slender 
axis with thin flat, green, leaf-like expansions. Examin- 
ing with the microscope the lower end of the axis, which is 
attached to the substratum, there are seen numerous brown 
colored threads more or less branched. (For nutrition of 
moulds, mushrooms, parasitic fungi, dodder, carnivorous plants, 
lichens, aquatic plants, etc., sec Tart III. Ecology.) 

171. The plant body. In the simpler forms of plant life, as in spirogyra 
and many of the algae and fungi, the plant body is no1 differentiated into 
parts. In many other cases the only differentiation is between the growing 
pari and the fruiting part. In the algae and fungi there is no differentiation 
into stem and leaf, though there is an approach to it in some of the higher 
forms. Where till— simple plant body is flattened, as in the sea-wrack, m- 
ulva, it is a frond. The Latin word fof frond is thallus, and this name i> 



NUTRITION ; MEMBERS PLANT BODY. 



73 



applied to the plant body of all the lower plants, the algae and fungi. The 
algae and fungi together are sometimes called the thallophytes^ or thallus 

plants. The word thallus i- also sometimes 
applied to the flattened body of the liver- 
worts. In the foliose liverworts and mos& - 
there i> an axis with Leaf-like expansions! 
These are believed by some to represent 
true stems and leaves, by others to represent 
a flattened thallus in which the margins are 
deeply and regularly divided, or in which 
the expansion has only taken place at regular 
intervals. 

^2L 




Fig. 63. 
Foliose liverwort ^Bazzania) showing dichotomous branching and overlapping leaves. 



172. Members of the plant body. — In the higher plants there is usually 
great differentiation of the plant body, though in many forms, as in the duck- 
weeds, it is a frond. While there is great variation in the form and func- 
tion of the members of the plant body, they are reducible to a few fundamental 
members. Some reduce these forms to three, the root, stem, and leaf, while 
others to two, the root and shoot, which is perhaps the better arrangement. 
Here the shoot is farther divided into stem and leaf, the leaf being a lateral 
outgrowth of the stem. The different forms of the members are usually des- 
ignated by special names, but it is convenient to group them in the single 
series. Examples are as follows: 

173. Stem series. 

Tubers, underground thickened stems, bearing buds and scale leaves; ex., 
Irish potato. 

Root -stocks, underground, usually elongated, bearing scales or bracts, and 
a leafy shoot; ex.. trillium, mandrake, etc. Root-stocks of the ferns bear 
expanded, green leaves. 

Runners, -lender, trailing, bearing bracts, and leafy stems as branches; 
ex., strawberry vines. 

Conns, underground, short, thick. Leaf bearing and scale bearing; ex., In- 
dian turnip. 



74 



PHYSIOLOGY. 



Bulbs, usually underground, short, conic 




Fig. 64. 

Female plant (gametophyte) of 
a moss (mnium), showing rhizoids 
below, and the tuft of leaves above, 
which protect the archegonia. 



leaf and scale bearing; ex., 
lily. 

Thorns, stout, thick, poorly developed bran- 
ches with rudiments of leaves (scales); ex., 
hawthorn. 

Tendrils, slender reduced stems. 

Flower axes (see morphology of the angio- 
sperms). 

174. Leaf series. — Besides the foliage leaves, 
the following are some of their modifications: 

Flower parts (see morphology of the angio- 
sperms). 

Bracts and scales, small, the former usually 
green (flower bracts), the latter usually chloro- 
phylless. Bud scales are sometimes green. 

Tendrils, modifications of the entire leaf 
(tendrils of the squash where the branched 
tendril shows the principal veins of the leaf), 
modification of the terminal pinnae of the leaf 
(vetch), etc. 

Spines (examples are found in the cacti, 
where the stem is enlarged and green, function- 
ing as a leaf). 

Other modifications occur as in the pitcher 
plant, insectivorous plants, etc. 

175. The root shows less modification. Be- 
sides normal roots, which are fibrous in most 
small plants and stout in the larger ones, some 
of the modifications are found in fleshy roots, 
where nourishment is stored (ex., dahlia, 
sweet potato, etc.), aerial roots (ex., poison 
ivy, the twining form), aerial orchids, etc. For 
modifications of roots due to symbiotic fungi, 
see chapter on Nutrition in Part III. 



CHAFFER XIII. 

GROWTH. 

176. By growth is usually meant an increase in the bulk of 
the plant accompanied generally by an increase in plant sub- 
stance. Among the lower plants growth is easily studied in 
some of the fungi. 

177. Growth in mucor. — Some of the gonidia (often called 
spores) may be sown in nutrient gelatine or agar, or even in 
prune juice. If the culture has been placed in a warm room, in 
the course of 24 hours, or even less, the preparation will be ready 
for study. 

178. Form of the gonidia. — It will be instructive if we first 
examine some of the gonidia which have not been sown in the cul- 
ture medium. We should note their rounded or globose form, as 
well as their markings if they belong to one of the species with 
spiny walls. Particularly should we note the size, and if possible 
measure them with the micrometer, though this would not be 
absolutely necessary for a comparison, if the comparison can be 
made immediately. Now examine some of the gonidia which 
were sown in the nutrient medium. If they have not already 
germinated we will note at once that they are much larger than 
those which have not been immersed in a moist medium. 

179. The gonidia absorb water and increase in size before 
germinating. — From our study of the absorption of water or 
watery solutions of nutriment by living cells, we will easily un- 
derstand the cause of this enlargement of the gonidium of the 
mucor when surrounded by the moist nutrient medium. The 
cell -sap in the spore takes up more water than it loses by diffu- 

75 



7 6 



/'// YSIOLOG V. 



sion, thus drawing water forcibly through the protoplasmic mem- 
brane. Since it does not filter OUl readily, the increase in 




Kig. 6s 
Spoils ol mucor, and different stages oi germination. 

quantity of the water in the cell produces a pressure from within 
which Stretches the membrane, and the elastic cell wall yields, 
dims the gonidium becomes larger. 

180. How the gonidia germinate. — We should find at this 
time many of the gonidia extended on one side into a tube-like 
process the length of which varies according to time and tempera- 
ture. Hie short process thus begun continues to elongate. This 
elongation of the plant is growth, or, more properly speaking, one 
of the phenomena of growth. 

181. The germ tube branches and forms the mycelium. — 
In the course of a day or so branches from the tube will appear. 
This branched form of the threads oi the fungus is, as we will 
remember, the mycelium. We can still see the point where 
growth started from the gonidium. Perhaps by this time several 
tubes have grown from a single one. The threads o\ the myce- 
lium near the gonidium, that is, the older portions of them, have 
increased in diameter as they have elongated, though this increase 

in diameter is bv no means so great as the increase in length. 
After increasing to a certain extent in diameter, growth in this 
direction ceases, while apical growth is practically unlimited, 
being limited onlj by the supply oi nutriment. 

182 Growth in length takes place only at the end of the 
thread. — If there were any branches ow the mycelium when the 



GROWTH. 77 

culture was first examined, we can now see that they remain 
practically the same distance from the gonidium as when they 
were first formed. That is, the older portions of the mycelium 
do not elongate. Growth in length of the mycelium is confined 
to the ends of the threads. 

183. Protoplasm increases by assimilation of nutrient 
substances. — As the plant increases in bulk we note that there 
is an increase in the protoplasm, for the protoplasm is very 
easily detected in these cultures of mucor. This increase in the 
quantity of the protoplasm has come about by the assimilation 
of the nutrient substance, which the plant has absorbed. The 
increase in the protoplasm, or the formation of additional plant 
substance, is another phenomenon of growth quite different from 
that of elongation, or increase in bulk. 

184. Growth of roots. — For the study of the growth of roots 
we may take any one of many different plants. The seedlings of 
such plants as peas, beans, corn, squash, pumpkin, etc., serve 
excellently for this purpose. 

185. Roots of the pumpkin. — The seeds, a handful or so, are 
soaked in water for about 12 hours, and then placed between 
layers of paper or between the folds of cloth, which must be kept 
quite moist but not very wet, and should be kept in a warm place. 
A shallow crockery plate, with the seeds lying on wet filter paper, 
and covered with additional filter paper, or with a bell jar, an- 
swers the purpose well. 

The primary or first root (radicle) of the embryo pushes its way 
out between the seed coats at the small end. When the seeds are 
well germinated, select several which have the root 4-5CW long. 
With a crow-quill pen we may now mark the terminal portion of 
the root off into very short sections as in fig. 66. The first mark 
should be not more than \mm from the tip, and the others not 
more than \mm apart. Now place the seedlings down on damp 
filter paper, and cover with a bell jar so that they will re- 
main moist, and if the season is cold place them in a warm room. 
At intervals of 8 or 10 hours, if convenient, observe them and 
note the farther growth o{ the root. 



78 



PHYSIOLOGY. 



186. The region of elongation. — While the root lias elon- 
gated, the region of elongation is not at the tip of flic roof. It lies 

a little distance back from the tip, beginning at 
about imm from the tip and extending- over 
an area represented by from 4-5 of the milli- 
meter marks. The 
root shown in fig. 66 
was marked at 10 A.M. 
on July 5. At 6 p.m. 
of the same day, 8 






Fig. 66. 

Root of germinating pumpkin, showing region of 

elongation just back of the tip. 



hours later, growth had taken place as shown in the middle 
figure. At 9 a.m. on the following day, 15 hours later, the 
growth is represented in the lower one. Similar experiments 
upon a number of seedlings gives the same result : the region o\ 
elongation in the growth of the root is situated a little distance 
back from the tip. Farther back very little or no elongation 
takes place, but growth in diameter continues for some time, as 
we should discover if we examined the roots of growing pump- 
kins, or other plants,- at different periods. 

187. Movement of region of greatest elongation. — In the 
region of elongation the areas marked oil do not all elongate 
equally at the same time. The middle spaces elongate most 
rapidly and the sj wees marked o(\ by the 6, 7, and 8 /;/;;/ marks 
elongate slowly, those farthest from the tip more slowly than the 
others, since elongation has nearly ceased here. The spaces 
marked off between the 2-4////'/ marks also elongate slowly, but 
soon begin to elongate more rapidly, since that region is becom- 
ing the region of greatest elongation. Thus the region of greatest 
elongation moves forward as the root grows, and remains ap- 
proximately at the same distance behind the tip. 

188. Formative region. — Lf we make a longitudinal section of the tip of a 
growing r<x>t of tin- pumpkin or other seedling, and examine it with the mi- 



GROWTH. 79 

croscope, we will see that there is a greal difference in the character of the 

cells of the tip and those in the region of elongation of the root. First there 
i- in the section a V-shaped cap of Loose cells which are constantly being 
sloughed off. Just back of this tip the cells are quite regularly isodiametric, 
that is, of equal diameter in all directions. They are also very rich in pro- 
toplasm, and have thin walls. This is the region of the root where new cells 
are formed by division. It is the formative region. The cells on the outside 
of this area are the older, and pass over into the older parts of the root and root 
cap. If we examine successively the cells back from this formative region 
we rind that they become more and more elongated in the direction of the 
axis of the root. The elongation of the cells in this older portion of the root 
explains then why it is that this region of the root elongates more rapidly 
than the tip. 

189. Growth of he stem. — We may use a bean seedling 
growing in the soil. At the junction of the leaves with the stem 
there are enlargements. These are the nodes, and the spaces on 
the stem between successive nodes are the internodes. We should 
mark off several of these internodes, especially the younger ones, 
into sections about $mm long. Now observe these at several 
times for two or three days, or more. The region of elongation 
is greater than in the case of the roots, and extends back farther 
from the end of the stem. In some young garden bean plants 
the region of elongation extended over an area of 40mm in one 
internode. 

190. Force exerted by growth. — One of the marvelous things connected 
with the growth of plants is the force which is exerted by various members of 
the plant under certain conditions. Observations on seedlings as they are 
pushing their way through the soil to the air often show us that considerable 
force is required to lift the hard soil and turn it to one side. A very striking 
illustration may be had in the case of mushrooms which sometimes make 
their way through the hard and packed soil of walks or roads. That succu- 
lent and tender plants should be capable of lifting such comparatively heavy 
weights seems incredible until we have witnessed it. Very striking illustra- 
tions of the force of roots are seen in the case of trees which grow in rocky 
situations, where rocks of considerable weight are lifted, or small rifts in 
large rocks are widened by the lateral pressure exerted by the growth of a 
root, which entered when it was small and wedged its way in. 

191. Grand period of growth. — Great variation exists in the rapidity of 
growth even when not influenced by ont-idr conditions. In our study of the 
elongation of the root we found that the cells just back of the formative region 



So 



PHYSIOLOGY. 



elongated -lowly at first. The rapidity of the elongation of these cells in- 
« reases until it reaches the maximum. Then the rapidity of elongation les- 
ls the cells come to lie farther from the tip. The period of maximum 
elongation here is the grand period of growth of these cells. 

192. fust as the c< lis exhibit a grand period of growth, so the members of 
the plant exhibit a similar grand period of growth. In the case of leaves, 
when the} are young the rapidity <>i growth is comparatively slow, then it 
increases, and finally diminishes in rapidity again. So it is with the stem. 
Winn tin- plant is young the growth is not so rapid; as it approaches middle 
age the rapidity of growth increases; then it de< lines in rapidity at the close 
of the season. 

193. Energy of growth. — Closely related to the grand period of growth is 
what is termed the energy of growth. This is manifested in the compara- 
tive size of the membersof a given plant. 
To take the sunflower for example, the 
lower and first leaves are comparatively 
small. As the plant grows larger the 
leaves are larger, and this increase in 
size of the leaves increases up to a maxi- 
mum period, when the size decreases 
until we reach the small leaves at the top 

of the stem. The grand period of growth 
of the leaves corresponds with the maxi- 
mum size of the leaves on the stem. 
The rapidity and energy of growth of the 
stem is also correlated with that of the 
leave-, and the grand period 
< it gr< >\\ th i- ci (incident with 
that of the leaves. It would 
be instructive to note it 
in the case of other plant- 
and also in tin- case "t 
fruits, 
grovt th "I the stem all of the i ells <'f a given 
igate simultaneously. For example the cells 
1 1 1 1 side are elongating more rapidly than the 
will cause the stem to bend slightly to the 




Fig. 67. 
Luxanometer (Oels) for measuring elongation of 
the stem during grow th. 



194. Nutation. 1 luring tl 
5( < tion "1 the tem do nol 1 l< 
.1 1 .i given mi >ment on the s< 
on the other sid< . I hi 
north. In .1 I- u moments later the cells on the west side are elongating more 
rapidly, and the stem 1 turned to the east; and ups oi cells in sue- 

on around the stem elongate more rapidl) than the others. This causes 
the tem to d< circle or ellipse about .1 central point. Since the re 

tion of the cell of th< t< m i g 1 adua lis in« >ving t< >\\ ard 
ih< in. tin hue oi elongation of the ( ells \\ In h is 



GROWTH. 8 1 

traveling around the stem docs so in a spiral maimer. In the same way. 
while the end of the stem is moving upward by the elongation of the cells, 
and at the same time is slowly moved around, the line which the end of tin- 
stem describes must be a spiral one. This movement oi the stem, which is 
common to all stems, leaves, and roots, is nutation* 

195. The importance oi nutation to twining stems in their search for a 
place of support, as well as for the tendrils on leaves or stems, will be seen. 
In the case of the root it is of the utmost importance, as the root makes its 
way through the soil, since the particles of soil are mote easily thrust aside. 
The same is also true in the case of many stems before they emerge from the 
soil. 



CHAPTER XIV. 

IRRITABILITY. 

196. We should now examine more carefully certain move- 
ments which the members of the plants exhibit. By this 
time we have probably observed that the direction which the 
root and stem take upon germination of the seed is not due to 
the position in which the seed happens to lie. Under normal 
conditions we have seen that the root grows downward and the 
stem upward. 

197. Influence of the earth on the direction of growth. — 
When the stem and root have been growing in these directions 
for a short time let us place the seedling in a horizontal position, 
so that the end of the root extends over an object of support in 
such a way that it will be free to go in any direction. It should 
be placed under a bell jar so as to prevent drying, or a germi- 
nated pea may be pinned to the lower side of a cork, which is 
then placed in the mouth of a bottle containing a little water. 
In the course of twelve to twenty-four hours the root which was 
formerly horizontal has turned the tip downward again. If we 
should mark off millimeter spaces beginning at the tip of the 
root, we should find that the motor zone, or region of curvature, 
lies in the same region as that of the elongation of the root. 

It was found by Knight, as a result o\ experiments, that the 
force which causes the roots to take the downward direction is 
gravity. This force is geotropi$m y which means a turning in- 
fluenced by the earth, and is applied to the growth movements 
of plants influenced by the earth, with regard to the direction 
of growth. GlOWth toward the earth is also termed progco/ro- 

82 



jrriiw n/Li r\ . 



33 



pistn. So the lateral growth of the secondary roots is termed 
diageotropism. 

The stem, on the other hand, which was placed in a horizontal 
position has become again erect. This tinning of the stem in 





Fig. 68. Fig. 69. 

Germinating pea placed in a hori- 
zontal position. 

Figs. 6S, 69. — Progeotropism of the pea root 



In 24 hours gravity has caused the root to 
turn downward. 



the upward direction takes place in the dark as well as in the 
light, as w T e can see if we start the experiment at nightfall, or 

place the plant in the dark. This up- 
ward growth of the stem is also influ- 
enced by the earth, and therefore is a 
case of geotropism. The special desig- 
nation in the case of upright stems is 
negative geotropism, or apo geotropism, or 
the stems are said 
to be apogeotropic. 




Fig. 70. 
Pumpkin seedling showing apogeotropism. Seedling at the left placed hori- 
zontally, in 24 hours the stem has become erect. 

If we place a rapidly growing potted plant in a horizontal 

position by laying the pot on its side, the ends of the shoots 

will soon turn upward again when placed in a horizontal 

position. Young bean plants growing in a pot began within 
two hours to turn the ends of the shoots upward. 



84 



PHYSIOLOGY. 



Horizontal leaves and shoots can be shown to be subject to 
the same influence, and are therefore diageolropic. 

198. Influence of light. — Not only is light a very important 
factor for plants during carbon conversion, it exerts great influ- 
ence on plant growth and movement. 

199. Retarding influence of light on growth. — We have 
only to return to the experiments performed in growing plants in 
the dark to see 
one of the influ- 
ences which light 
exerts on plants. 
The plants grown 
in the dark were 
longer and more 
slender than those 
grown in the light. 
Light then has a 
retarding influ- 
ence on the elong- 
ation of the stem. 

200. Influence 
of light on direc- 
tion of growth. — While we are growing 
seedlings, the pots or boxes of some of them 
should be placed so that the plants will 
have a one-sided illumination. This can Radish seedlings grown in 

, the light, shorter, stouter, and 

be done by placing them near an open green in color. Growth re- 

. . tarded by light. 

window, m a room with a one-sided illu- 
mination, or they may be placed in a box closed on all sides 
but one which is facing the window or light. In 12-24 hours, 
or even in a much shorter time in some cases, the stems of the 
seedlings will be directed toward the source of light. This 
influence exerted by the rays of light is heliotropism, a turning 
influenced by the sun or sunlight. 

201. Diaheliotropism. — Horizontal leaves and shoots are 
diaheliotropic as well as diageotropic. The genera] direction 




Fig. 71. 

Radish seedlings grown in the 

dark, long, slender, not green. 



IRRITABILITY. 



85 



which leaves assume under this influence is that of placing them 
with the upper surface perpendicular to the rays of light which 
fall upon them. Leaves, then, exposed to 
the brightly lighted sky are, in general, 
horizontal. This position is taken in direct 
response to the 
stimulus of light. 
The leaves of plants 
with a one-sided Mu- 
ni inati o n , 
as can be 
seen by 
trial, are 
turned with 
their upper 

Seedling of castor-oil Dean, before and after * l 

surfaces to- 
ward the 
source of light, or perpendicular to the in- 
cidence of the light rays. In this way 
light overcomes for the time being the 
direction which growth gives to the leaves. 
The so-called " sleep" of plants is of 
course not sleep, though the leaves " nod," 
or hang downward, in many cases. There 
are many plants in which we can note 
this drooping of the leaves at nightfall, and in order to prove 
that it is not determined by the time of day we can resort to 

a well-known ex- $=——=================1 

periment to induce HP 

this condition dur- 
ing the day. The 
plant which has 
been used to illus- 
trate this is the sun- 
flower. Some of 
these plants, which 





Fig. 74- 

Dark chamber with opening at one side to show heliotropism. 
(After Schleichert.) 



86 



PHYSIOLOGY. 



were grown in a box, when they were about 35cm high were 
covered for nearly two days, so that the light was excluded. 
At midday on the second day the box was removed, and the 
leaves on the covered plants are well represented by fig. 75, which 
was made from one of them. The leaves of the other plants 
in the box which were not covered were horizontal, as shown 
by fig. 76. Now on leaving these plants, which had exhibited 




Fig. 76. 
Sunflower plant removed from 
darkness, leaves extending under 
influence of light (diaheliotro- 
pism.) 

induced " sleep" move- 
ments, exposed to the light 
they gradually assumed 
the horizontal position again. 

202. Epinasty and hyponasty. — During 
the early stages of growth of many leaves, 
as in the sunflower plant, the direction of 
growth is different from what it is at a later 
period. The under surface of the young 
leaves grows more rapidly in a longitudinal 
direction than the upper side, so that the 
leaves are held upward close against the 
hud at the end of the stem. This is termed 
hyponasty, or the leaves are said to be 
hyponastic. Later the growth is more rapid 
on the upper side and the leaves turn downward or away from the bud. 
Tin's is termed epinasty, or the haves are -aid to be epinastic* This is shown 
by the night position of the leaves, or in the induced "sleep "of the sun- 



Fig. 75- 
Sunflower plant. Epinastic con- 
dition of leaves induced during the 
day in darkness. 



IRRITABILITY. 



87 



flower plant in the experiment detailed above. The day position of the 
leaves on the other hand, which is more or less horizontal, is induced because 
of their irritability under the influence of light, the inherent downward or 
epinastic growth is overcome for the time. Then at nightfall or in darkness, 
the stimulus of light being removed, the leaves assume the position induced 
by the direction of growth. 

In the case of the cotyledons of some plants it would seem that the growth 
was hyponastic even after they have opened. The day position of the coty- 




Squash seedling. 



Fig. 77. 

Position of cotyledons in 
light. 



Fig. 

Squash seedling. Position of cotyledons in 
the dark. 



ledons of the pumpkin is more or less horizontal, as shown in fig. 77. At 
night, or if we darken the plant by covering with a tight box, the leaves 
assume the position shown in fig. 78. 

While the horizontal position is the general one which is assumed by 
plants under the influence of light, their position is dependent to a certain 
extent on the intensity of the light as well as on the incidence of the light 
rays. Some plants are so strongly heliotropic that they change their posi- 
tions all during the day. 

203. Leaves with a fixed diurnal position. — Leaves of some plants when 
they are developed have a fixed diurnal position and are not subject to 



88 



PHYSIOLOG V. 



variation. Sucb leaves tend to arrange themselves in a vertical or para 
heliotropic position, in which the surfaces are nol exposed (<> the incidence 
oi lighl of the greatest intensity, l>ui to the incidence of the rays of diffused 
light. Enteresting cases of the fixed position of leaves are found in the so- 
called eoinpass plants (like Silphiinn laciniatum, l.actuca scariola, etc.). In 

these the horizontal Leaves arrange themselves \\ ith the surfaces vertical, and 

also pointing north and south, so that the surfaces lace east and wist. 

204. Importance of these movements. Not only are the Leaves placed in 
.1 position favorable for the absorption of the rays of light which are con 
cerned in making carbon available lor food, bul they derive other forms of 

energy from the Light, as heat, which is absorbed during the day. Then 

with the nocturnal position, the leaves being drooped down toward the stem, 

or with the margin toward the sky, or w ith the cotyledons as in the pump- 
kin, castor oil bean, etc., clasped Upward together, the loss of heat by 
radiation is I'ss than it WOUld be if the upper Surfaces of the leaves were 
exposed to the sk\ . 

205. Influence of light on the structure of the leaf. In our study of the 

structure of a leal we found that in the ivy leaf the palisade cells were on 

the upper surface. This is the case with a 

greal many Leaves, and is the normal arrange 
' ment of u dorsiventral " leaves which are dia- 

heliotropic. Leaves which are parahcliotropic 
tend to Liave palisade cells on both surfaces. 

The palisade layer of cells as we have seen is 
made up of cells Lying very close- together, and 
they thus prevent rapid evaporation. They 

also check to some extent the entrance of the 
rays of light, at least more so than the loose 

spongy parenchyma cells do. Leaves developed 

in the shade have looser palisade and paren 
Chyma cells. In the case of some plants, it 

we turn over a very young leaf, so that the 
under side will be uppermost, this side will 
develop the palisade layer. This shows that 
light has a great influence on the structure of 
the leaf. 

206. Movement influenced by contact. In 

the case n\ tendrils, twining leaves, or stems, 

the irritability to contact is shown in a move 
ment of the tendril, etc., toward the object in 

touch. This causes the tendril or stem to coil 

around the object foi support, rhe stimulus is also extended down the part 
,,i the tendril belov\ the point <>i contact (see fig. 79), and that part coils 




Fig. :«>. 
iling tendi il «>i bi \<>n\ 



JRRITABILIT K. 



8 9 



up like a wire coil spring, thu drawing the leaf or branch from which the 
tendril gro\» closer to the object oi upport. Thi coil between the object 
"i support and the plant is also \<t\ important in easing up the plant when 
subje< 1 to violent gusts ot wind which might tear the plant from it upport 
were it not for the yielding and springing motion oi thi coil. 

207. Sensitive plants. — These plants are remarkable lor the 
rapid response to stimuli. Mimosa pudica is an excellent plant 
to stud) for tins purpose. 

208. Movement in response to stimuli II we pinch with 
the forceps one of the terminal leaflets, or tap it with a pencil, 
the two end leaflets fold above the " vein" of tin- pinna. This 

is immediately followed 
>y the movement of the 
iext pair, and so on as 
shown in fig. 81 , until all 
he leaflets on this pinna 
ire closed, then thestimu 
lus travels down the 

ot her pinna- in a simi- 
lar manner, and 
Fig. 80. 

ti\e plant lr.it 
in normal position. 





Fig. 81. 
Pinna fold- 
ing up aftei 
stimuli] . 

soon the pinnae approximate each other and 

the leaf then drops downward as shown in , *" : 

1 Later .ill the pinnae 

fig, 82. The normal position of the leaf is folded and lea£ drooped. 

shown in fig. So. If we jar the plant by striking it or by jarring 
the pot in which it is grown all the leaves quickl) collapse into 
the position shown in fig. 82. Ii we examine the leaf now we 
will see minute cushions at the base of each leaflet, at the 
junction of the pinnae with the petiole, and a larger one at the 
junction of the petiole with the stem. We will also note that 
the movement resides in these cushions, 



9° 



PHYSIOLOGY. 



209. Transmission of the stimulus. — The transmission of 
the stimulus in this mimosa from one part of the plant has been 
found to be along the cells of the bast. 

210. Cause of the movement. — The movement is caused by 
a sudden loss of turgidity on the part of the cells in one portion 
of the pulvinus, as the cushion is called. In the case of the 
large pulvinus at the base of the petiole this loss of turgidity is 
in the cells of the lower surface. There is a sudden change in 
the condition of the protoplasm of the cells here so that they 
lose a large part of their water. This can be seen if with a sharp 
knife we cut off the petiole just above the pulvinus before move- 
ment takes place. A drop of liquid exudes from the cells of the 
lower side. 



211. Paraheliotropism of the leaves of the sensitive plant. — If the mimosa 

plant is placed in very intense light the leaflets will turn their edges toward 
the incidence of the rays of light. This is also true of other plants in 
intense light, and is paraheliotropism. Transpiration is thus lessened, and 
chlorophyll is protected from too intense light. 

We thus see that variations in the intensity of light have an important 
influence in modifying movements. Variations in temperature also exert 

a considerable influence, rapid 
elevation of temperature causing 
certain flowers to open, and 
falling temperature causing 
them to close. 

212. Sensitiveness of insec- 
tivorous plants. — The Venus 
fly-trap (Dionaea muscipula)and 
the sundew (drosera) are in- 
teresting examples of sensitive 
plants, since the leaves close in 
response to the stimulus from 
insects. 




Fig 
Leaf of Venus tlv 
trap (Dionaea musci- 
puia). showing winged 

fietiolc and loomed 
obes. 



Fig. 84. 
1 eaf of Drosera ro- 
tundifolia, some of the 
glandular hairs Folding 
inward as a result ol a 
stimulus. 



213. Hydrotropism . — 

Roots are sensitive to mois- 
ture. They will turn toward moisture. 'This is of the greatest 
importance for the well-being of the plant, since the roots will seek 
those place in the soil where suitable moisture is present. On 



IRRITABILITY, 9 1 

the other hand, if the soil is too wet there is a tendency for the 
roots to grow away from the soil which is saturated with water. 
In such cases roots are often seen growing upon the surface of 
the soil so that they may obtain oxygen, which is important for 
the root in the processes of absorption and growth. Plants then 
may be injured by an excess of water as well as by a lack of 
water in the soil. 

214. Temperature. — In the 1 xperiments which have thus far been carried 
on it will probably have been noted that the temperature has much to do 
with the Length of time taken for seeds to germinate. It also influences the 
rate of growth. The effed of different temperatures on the germination of 
seed can be very well noted by attempting to germinate some in room 
various temperatures. It will be found, other conditions being equal, that 
in a moderately warm room, or even in one quite warm, 25-30 degrees cen 
tigrade, germination and growth goes on more rapidly than in a COOl room, 
and hen- mure rapidly than in one which is decidedly cold. Tn the case of 
most plants in temperate climates, growth may go on at a temperature hut 
little above freezing, but few will thrive at this temperature. 

215. i! we place dry peas or beans in a temperature of about 70" C. for 15 
minutes they will not be killed, but if they have been thoroughly soaked in 
water and then placed at this temperature they will be killed, or even at a 
somewhat lower temperature. The same seeds in the dry condition will 
withstand a temperature of io° C. below, but if they are first soaked in water 
this low temperature will kill them. 

216- In order to see the effect of freezing we may thoroughly freeze a sec- 
tion of a beet root, and after thawing it out place it in water. The water is 
colored by the cell-sap which escapes from the cells, just as we have seen it 
does as a result of a high temperature, while a section of an unfrozen beet 
placed in water will not color it if it was previously washed. 

If the slice of the beet is placed at about 6o° C. in a shallow glass v< 1 L, 
and covered, ice will be formed over the surface. If we examine it with the 
microscope ice crystals will be seen formed on the outside, and these will 
not be colored. The water for the formation <>i the cry-tab came from the 
cell-sap, but the concentrated solutions in the sap were not withdrawn by 
the freezing over the surface. 

217. If too much water is not withdrawn from the cells of many plant- in 
freezing, and they are thawed (nit slowly, the water which was withdrawn 
from the cells will be absorbed again and the plant will not be killed. I>ut 
if the plant i- thawed out quickly the water will not be absorbed, but will 
remain on the surface and evaporate. Seine will also remain in the inter- 
cellular spaces, and the plant will die. S<>ni» plants, however, no matter how 



92 PHYSIOLOGY. 

slowly they are thawed out, are killed after freezing, as the leaves of the 
pumpkin, dahlia, or the tubers of the potato. 

218. It has been found that as a general rule when plants, or plant parts, 
contain little moisture they will withstand quite high degrees of tempera- 
ture, as well as quite low degrees, but when the parts are filled with sap or 
water they are much more easily killed. For this reason dry seeds and the 
winter buds of trees, and other plants, because they contain but little water, 
are better able to resist the cold of winters. But when growth begins in the 
spring, and the tissues of these same parts become turgid and filled with 
water, they are quite easily killed by frosts. It should be borne in mind, 
however, that there is great individual variation in plants in this respect, 
some being more susceptible to cold than others. There is also great varia- 
tion in plants as to their resistance to the cold of winters, and of arctic 
climates, the plants of the latter regions being able to resist very low tem- 
peratures. We have examples also in the arctic plants, and those which 
grow in arctic climates on high mountains, of plants which are able to carry 
on all the life functions at temperatures but little above freezing. 



MORPHOLOGY AND LIFE HISTORY OF REPRE- 
SENTATIVE PLANTS. 

CHAFFER XV. 

SPIROGYRA. 

219. In our study of protoplasm and some of the processes of 
plant life we became acquainted with the general appearance of 
the plant spirogyra. It is now a familiar object to us. And in 
taking up the study of representative plants of the different 
groups, we shall find that in knowing some of these lower plants 
the difficulties of understanding methods of reproduction and 
relationship are not so great as they would be if we were entire- 
ly ignorant of any members of the lower groups. 

220. Form of spirogyra. — We have found that the plant 
spirogyra consists of simple threads, with cylindrical cells 
attached end to end. We have also noted that each cell of the 
thread is exactly alike, with the exception of certain " hold- 
fasts " on some of the species. If we should examine threads in 
different stages of growth we should find that each cell is capable 
of growth and division, just as it is capable of performing all the 
functions of nutrition and assimilation. The cells of spirogyra 
then multiply by division. Not simply the cells at the ends of 
the threads but any and all of the cells divide as they grow, and 
in this way the threads increase in length. 

221. Multiplication of the threads.- In studying living material of this 
plant we have probably noted that the threads often become broken by two of 
the adjacent cells of a thread becoming separated. This may be and isaccom- 

93 



94 



MORPHOLOG Y. 





<m 



plished in many cases without any injury to the cells. In this manner the 
threads or plants of spirogyra, if we choose to call a thread a 
plant, multiply, or increase. In this breaking of a thread the 
cell wall which separates any two cells splits. If we should 
examine several species of spirogyra we would probably find 
threads which present two types as regards the character of 
the walls at the ends of the cells. In fig. 85 we see that the 
ends are plain, that is, the cross walls are all straight. But 
in some other species the inner wall of the cells presents a 
peculiar appearance. This inner wall at the end of the 
cell is at first straight across. But it soon becomes folded 
back into the interior of its cell, just as the end of an 
empty glove finger may be pushed in. Then the infolded 
end is pushed partly out again, so that a peculiar figure is 
the result. 

222. How some ol the threads break. — In the separation 
of the cells of a thread this peculiarity is often of advan- 
tage to the plant. The cell-sap within the protoplasmic 
membrane absorbs water and the pressure pushes on the 
ends of the infolded cell walls. The inner wall being so 
much longer than the outer wall, a pull is exerted on the 
latter at the junction of the cells. Being weaker at this 
point the outer wall is ruptured. The turgidity of the two 
cells causes these infolded inner walls to push out suddenly 
as the outer wall is ruptured, and the thread is snapped 
apart as quickly as a pipe-stem may be broken. 

223. Conjugation of spirogyra. — Under cer- 
tain conditions, when vegetative growth and 
multiplication cease, a process of reproduction 
takes place which is of a kind termed sexual repro- 
duction. If we select mats of spirogyra which 
have lost their deep green color, we are likely to 
find different stages of this sexual process, which 
in the case of spirogyra and related plants is called 

Fig - 85 ' conjugation. A few threads of such a mat we 

Thread of spircr so ^ 

gyra, showing lone should examine with the microscope. If the 

cells, chlorophyll 

band, nucleus, material is in the ri^ht condition we will see in 

strands of proto- ° 

plasm, and the certain of the cells an oval or elliptical body. 

granular wall layer 

of protoplasm. If we note carefully the cells in which these oval 

bodies are situated, there will be seen a tube at one side which con- 



Si, 






SPIROGYRA. 



95 



nects with an empty cell of a thread which lies near as shown in 

fig. 86. If we search through the material we may see other threads 

connected in this ladder fashion, in which 

the contents of the cells are in various stages 

of collapse from what we have seen in the 

growing cell. In some the protoplasm and 

chlorophyll band have moved but little from 

the wall ; in others it forms a mass near the 

center of the cell, and again in others we 

will see that the contents of the cell of one 

of the threads has moved partly through the 

tube into the cell of the thread with which it 

is connected. 

224. This suggests to us that the 
oval bodies found in the cells of one 
thread of the ladder, while the cells 
of the other thread were empty, are 
formed by the union of the contents 
of the two cells. In fact that is what 
does take place. This kind of union 
of the contents of two similar or nearly 
similar cells is conjugation. The oval 
bodies which are the result of this 
conjugation are zygotes, or zygospores. 
When we are examining living ma- 
terial of spirogyra in this stage it is jj 
possible to watch this process of con- 
jugation. Fig. 87 represents the differ- 
ent stages of conjugation of spirogyra. 

225. How the threads conjugate, or join. — The cells of two 
threads lying parallel put out short processes. The tubes from 
two opposite cells meet and join. The walls separating the con- 
tents of the two tubes dissolve so that there is an open communi- 
cation between the two cells. The contents of each one of these 
cells which take part in the conjugation is a gamete. The one 
which passes through the tube to the receiving cell is the supply- 




Fig. 86. 
Zygospores of spirogyra. 



9 6 



MOKPHOLOG Y. 



ing gamete, while that of the receiving cell is the receiving 
gamete, 

226. How the protoplasm moves from one cell to another. — Before any 
movement of the protoplasm of the supplying cell takes place we can see 




Fig. 87. 

Conjugation in spirogyra ; from left to right beginning in the upper row is shown the 
gradual passage of the protoplasm from the supplying gamete to the receiving gamete. 

that there is great activity in its protoplasm. Rounded vacuoles appear 
which increase in size, are filled with a watery fluid, and swell up like a 
vesicle, and then suddenly contract and disappear. As the vacuole disap- 
pears it causes a sudden movement or contraction of the protoplasm around 
it to take its place. Simultaneously with the disappearance of the vacuole 
the membrane < I the protoplasm is separated from a part of the wall. This 
is probably brought about by a sudden loss of some of the water in the cell- 
sap. These activities go on. and the protoplasmic membrane continues to 
-lip away from the wall. Every now and then then- is a movement by 
which the protoplasm i^ moved a short distance. It is moved toward the 
tube and finally a portion of it with one end of the chlorophyll band begins 
to move into the tube. About this time the vacuoles cm be seen in an 

tctive condition in tin- receptive cell, At short intervals movement con- 



SPIROGYRA. 



97 



tinues until the content <>f the supplying cell has passed over into that of the 
receptive cell. The protoplasm of this one is now slipping away from the 

cell wall, until finally the two masses round up into the one zygospore. 

227. The zygospore.- Thi- zygospore now acquires a thick wall which 
eventually becomes brown in color. The chlorophyll color lades out. an 1 a 
large part of the protoplasm passes into an oily substance which makes it 
more resistant to conditions which would be fatal to the vegetative threads. 
The zygospores are capable therefore of enduring extremes of cold and dry- 
ness which would destroy the thread-. They pass through a •• resting" 
period, in which the water in the pond may be frozen, or dried, and with the 
oncoming of favorable conditions for growth in the spring or in the autumn 
they germinate and produce the green thread again. 

228. Life cycle. — The growth of the spirogyra thread, the conjugation of 
the gametes and formation of the zygospore, and the growth of the thread 
from the zygospore again, makes what is called a complete life cycle. 

229. Fertilization. — While conjugation results in the fusion of the two 
masses of protoplasm, fertilization is accomplished when the nuclei of the 
two cells come together in the zygospore and fuse into a single nucleus. The 








Fig. 88. 
Fertilization in spirogyra : shows different stages of fusion of the two nuclei, with mature 
zygospore at right. (After Overton.) 

different stages in the fusion of the two nuclei of a recently formed zygospore 
are shown in figure 88. 

In the conjugation of the two cells, the chlorophyll band of the supplying 
cell is said to degenerate, so that in the new plant the number of chlorophyll 
bands in a cell is not increased by the union of the two cells. 

230. Simplicity of the process. — In spirogyra any cell of the thread 
may form a gamete (excepting the holdfasts of some species). Since all of 
the cells of a thread are practically alike, there i- no structural difference 
between a vegetative cell and a cell about to conjugate. The difference is a 
physiological one. All the cells are capable of conjugation if the physiolog- 
ical conditions are present. All the cells therefore are potential garnet 
(Strictl\- -peaking the wall of the cell is the gametangium, while the content- 
make the gamete.) 

While there i- sometimes a slight difference in size between tin- coiijngat 



98 



MORPHOLOGY. 



ing cells, and the supplying cell may be the smaller, this is not general. We 
say, therefore, that there is no differentiation among the gametes, so that 
usually before the protoplasm begins to move one cannot say which is to be 
the supplying and which the receiving gamete. 

231. Position of the plant spirogyra. — From our study then we see that 
there is practically no differentiation among the vegetative cells, except 
where holdfasts grow out from some of the cells for support. They are all 
alike in form, in capacity for growth, division, or multiplication of the 
threads. Each cell is practically an independent plant. There is no differ- 
entiation between vegetative cell and conjugating cell. All the cells are 
potential gametes. Finally there is no structural differentiation between the 
gametes. This indicates then a simple condition of things, a low grade of 
organization. 

232. The alga spirogyra is one of the representatives of the lower algae 
belonging to the group called Conjugate. Zygnema with star-shaped chloro- 
plasts, mougeotia with straight or sometimes twisted chlorophyll bands, be- 
long to the same group. In the latter genus only a portion of the protoplasm 
of each cell unites to form the zygospore, which is located in the tube between 
the cells. 




Fig. 89. 
( losterium. 




Fig. 90. 
Micrasterias. 






Fig. 91. 
Xanthidium. 




Fig. 94. 
( losmarium. 



233. The desmids also belong to the same group. The desmids usually live 
as separate cells. Man} of them are beautiful in form. They grow entangled 
among other algae, or on the surface of aquatic plants, or on wet soil. Sev- 
eral genera are illustrated in figures 89 94. 



CHAPTER XVI. 

CEDOGONIUM. 

234. (Edogonium is also an alga. The plant is sometimes 
associated with spirogyra, and occurs in similar situations. Our 
attention was called to it in the study of chlorophyll bodies. 
These we recollect are, in this plant, small oval disks, and thus 
differ from those in spirogyra. 

235. Form of cedogonium. — Like spirogyra, cedogonium 
forms simple threads which are made up of cylindrical cells 
placed end to end. But the plant is very different from any 
member of the group to which spirogyra belongs. In the first 
place each cell is not the equivalent of an individual plant as in 
spirogyra. Growth is localized or confined to certain cells of 
the thread which divide at one end in such a way as to leave a 
peculiar overlapping of the cell walls in the form of a series of 
shallow caps or vessels (fig. 95), and this is one of the character- 
istics of this genus. Other differences we find in the manner of 
reproduction. 

236. Fruiting stage of cedogonium. — Material in the fruiting 
stage is quite easily obtainable, and may be preserved for study 
in formalin if there is any doubt about obtaining it at the time 
we need it for study. This condition of the plant is easily de- 
tected because of the swollen condition of some of the cells, or 
by the presence of brown bodies with a thick wall in some of the 
cells. 

237. Sexual organs of oedogonium. Oogonium and egg. — 
The enlarged cell is the oogonium, the wall of the cell being the 
wall of the oogonium. (See f[g. 96.) The protoplasm inside, before 

99 



IOO 



MORPHOLOGY, 



fertilization, is the egg cell. In those cases where the brown body 

with a thick wall is present fertilization has taken place, and this 

body is the fertilized egg, or oospore. It contains 

large quantities of an oily substance, and, like 




Fig. 95- 

Portion o f 
thread of cedo- 
gonium, show- 
ing chlorophyll 
grains, and pe- 
culiar cap cell 
walls. 




I' ig. 96. 
(Edogonium undulatum, with oogonia and dwarf males; 
the upper oogonium at the right has a mature oospore. 



the fertilized egg of spirogyra and vaucheria, is able to with- 
stand greater changes in temperature than the vegetative stage, 
and can endure drying and freezing for some time without 
injury. 

In the oogonium wall there can frequently be seen a rift near 
the middle of one side, or near the upper end. This is the 



CEDOGONIUM. 



IOI 



opening through which the spermatozoid entered to fecundate 
the egg. 

238. Dwarf male plants. — In some species there will also be 
seen peculiar club-shaped dwarf plants attached to the side of the 
oogonium, or near it, and in many cases the end of this dwaif 
plant has an open lid on the end. 

239. Antheridium. — The end cell of the dwarf male in such 
species is the antheridium. In other species the spermatozoids 
are developed in different cells (antheridia) of the same thread 
which bears the oogonium, or on a different thread. 



240. Zoospore stage of cedogonium. — The egg after a period of rest starts 
into active life again. In doing so it does not develop the thread-like plant 
directly as in the case of vaucheria and spirogyra. It first divides into four 
zoospores which are exactly like the zoogonidia in form. (See fig. 103.) 
These germinate and develop the thread form again. This is a quite re- 
markable peculiarity of cedogonium when compared with either vaucheria 
or spirogyra. It is the introduction of an intermediate stage between the 
fertilized Qgg and that form of the plant which bears the sexual organs, and 
should be kept well in mind. 

241. Asexual reproduction. — Material for the study of this stage of cedo- 
gonium is not readily obtainable just when we wish it for study. But fresh 
plants brought in and placed in a 
quantity of fresh water may yield 
suitable material, and it should be 
examined at intervals for several 
days. This kind of reproduction 
takes place by the formation of 
zoogonidia. The entire contents 
of a cell round off into an oval 
body, the wall of the cell breaks, 
and the zoogonidium escapes. It 
has a clear space at the small 
end. and around this clear space 
is a row or crown of cilia as shown in fig. 97 
the zoogonidium swims around for a time, then settles down on some object of 
support, and several slender holdfasts grow out in the form of short rhizoids 
which attach the young plant. 

242. Sexual reproduction. Antheridia. — The antheridia are short cells 
which are formed by one of the ordinary cells dividing into a number of 
disk-shaped ones as shown in fig. 98. The protoplasm in each antheridium 





Fig. 97. 
Zoogonidia of cedogonium escaping. 
At the right one is germinating and 
forming the holdfasts, by means of which 
these algae attach themselves to objects 
for support. (After Pringsheim.) 

Bv the vibration of these cilia 



102 



MORPHOLOGY. 



forms two spermatozoids (sometimes only one) which are of the same form as 
the zoogonidia but smaller, and yellowish instead of green. In some species 

a motile body intermedi- 
ate in size and color be- 
tween the spermatozoids 
and zoogonidia is first 
formed, which after 
swimming around comes 
to rest on the oogonium, 
or near it, and develops 
what is called a "dwarf 
male plant " from which 
the real spermatozoid is 
produced. 

Portion of thread of oedo- ' ° 

gonium showing upper half oogonia are formed di- 
of egg open, and a sperma- ,, r r Al 

tozoid ready to enter. (After rectl y f ™m one of the 
Oltmans). vegetative cells. In most 

species this cell first enlarges in diameter, so that it is easily detected. The 
protoplasm inside is the egg cell. The oogonium wall opens, a bit of the 
protoplasm is emitted, and the spermatozoid then enters and fertilizes it 
(fig. 99). Now a hard brown wall is formed around it, and, just-as in spirogyra 




Fig. 98. 
Portion of thread 
O f cedogonium 
showing antheridia 





Fig. 100. 
Male nucleus just entering 
egg at left side. 

Figs. 100-102.— 




Fig. 101. Fig. 102. 

Male nucleus fusing with The two nuclei fused, and 
female nucleus. fertilization complete. 

Fertilization in cedogonium. (After Oltmans^. 



and vaucheria, it passes through a resting period. At the time of germination 
it does not produce the thread-like plant again directly, but first forms four 
zoospores exactly like the zoogonidia (fig. 103). These zoospores then 
germinate and form the plant. 

244. (Edogonium compared with spirogyra. — Now if we compare cedo- 
gonium with spirogyra, as we did in the case of vaucheria, we will find here 
also that there is an advance upon the simple condition which exists in spiro- 
gyra. Growth and division of the thread is limited to certain portions. The 
sexual organs are differentiated. They usually differ in form and size from 
the vegetative cells, though the oogonimn is simply a changed vegetative 



CEDOGONIUM. 



103 



cell. The sexual organs are differentiated among themselves, the antheridium 
is small, and the oogonium Large. The gametes are also differentiated in 

size, and the male gamete is motile, and carries in it- body the nucleus 
which fuses with the nucleus of the egg cell. 

But a more striking advance is the tact that the fertilized egg doe- not 





Fig. 103. 

Fertilized egg of oedogonium after a period of rest escaping from the wall of the oogonium, 
and dividing into the four zoospores. (After Juranyi.) 




produce the vegetative thread of oedogonium directly, but first forms four 
zoospores, each of which is then capable of developing into the thread. On 
the other hand we found 
that in spirogyra the zygo- 
spore develops directly 
into the thread form of the 
plant. 

245. Position of oedo- 
gonium. — CEdogonium is 
one of the true thread-like 
algae, green in color, and 
the threads are divided 
into distinct cells. It. 
along with many relatives, 
was once placed in the old 

genus conferva. These are all now placed in the group 
CcmfervoidecE, that is, the conferva -like algcr. 

246. Relatives of oedogonium. — Many other genera Portion of chaetophora 
are related to oedogonium. Some consist of simple 

threads, and others of branched threads. An example of the branched 
forms is found in chaetophora, represented in figures 104, 105. This plant 
grows in quiet pools or in slow-running water. It is attached to sticks, rocks, 
or to larger aquatic plants. Many threads spring from the same point of 
attachment and radiate in all direction^. This, together with the branching 
of the threads, makes a small, compact, greenMn rounded mass, which is 



Fig. 104. 
Tuft of chaeto- 
phora, natural 
size. 




1 04 MORPHOLOG y. 

held firmly together by a gelatinous substance. The masses in this species 
are about the size of a small pea, or smaller. Growth takes place in chse- 
tophora at the ends of the threads and branches. That is, growth is api- 
cal. This, together with the branched threads and the tendency to form 
cell masses, is a great advance of the vegetative condition of the plant upon 
that which we find in the simple threads of cedogonium. 



CHAPTER XVII. 

VAUCHERIA. 

247. The plant vaucheria we will remember from our study 
in an earlier chapter. It usually occurs in dense mats floating 
on the water or lying on damp soil. The texture and feeling of 
these mats remind one of "felt," 
and the species are sometimes called 
the " green felts." The branched 
threads are continuous, that is there 
are no cross walls in the vegetative 
threads. This plant multiplies it- 
self in several ways which would 
be too tedious to detail here. But 
when fresh bright green mats can be 
obtained they should be placed in 
a large vessel of water and set in 
a cool place. Only a small amount 
of the alga should be placed in a 
vessel, since decay 
will set in more 
rapidly with a large t 
quantity. For 

J Fig. 106. 

J Portion of branched thread of vaucheria. 

should look for 

small green bodies which may be floating at the side of the vessel 

next the lighted window. 

248. Zoogonidia of vaucheria. — If these minute floating green bodies are 
found, a small drop of water containing them should be mounted for exami- 

105 




io6 



MORPHOLOG Y. 



nation. If they are rounded, with slender hair-like appendages over the 
surface, which vibrate and cause motion, they very likely are one of the 
kinds of reproductive bodies ofvaucheria. The hair-like appendages are 
cilia, and they occur in pairs, several of them distributed over the surface. 
These rounded bodies are gonidia, and because they are motile they are 
called zoogonidia. 

By examining some oi the threads in the vessel where they occurred we 
may have perhaps an opportunity to see how they are produced. Short 
branches are formed on the threads, and the contents are separated from 
those of the main thread by a septum. The protoplasm and other contents of 
this branch separate from the wall, round up into a ma^, and escape through 
an opening which i> formed in the end. Here they swim around in the 
water lor a time, then come to rest, and germinate by growing out into a 
tube which forms another vaucheria plant. It will be observed that this 
kind of reproduction is not the result of the union of two different parts of 
the plant. It thus differs from that which is termed sexual reproduction. A 
small part of the plant -imply becomes separated from it a- a special body, 
and then grows into a new plant, a sort of multiplication. This kind of re- 
production has been termed asexual reproduction. 

249. Sexual reproduction in vaucheria. — The organs which are concerned 
in -exual reproduction in vaucheria are very readily obtained lor study if 
one collects the material at the right season. The}' are found quite readily 
during the spring and autumn, and may be preserved in formalin for study 
at any season, if the material cannot be collected fresh at the time it i> 
desired for study, fine material for study often occurs on the soil of pots in 

greenhouses during the winter. 
Whilethe zoogonidia are more 
apt to be found in material 
which is quite green and fresh- 
ly growing, the sexual organs 

ayo usually more abundant 

when the thread- appear some- 
vvhal yeVowish, or yellow 
green. 







r?r-*?r 




Fig, 107 

,in<l 



gonium "i Vau< hi 1 
1 1 intents ol thread b\ ■ 



250. Vaucheria sessi- 
lis ; the sessile vauche- 
ria. — In tin's plant the 
sexual organs are sessile, 

thai is the) are not borne on a stalk as in some other species. 

The sexual organs usually occur several in a group. Fig. 107 

represents a portion of a fruiting plant. 



\ '. »ung .mtli 1 idiun 
■,ili . I., fore •< parati< 
■ eptum 



VAUCHERIA. 



107 



251. Sexual organs of vaucheria. Anther idium. — The 
antheridia arc short, slender, curved branches from a main 
thread. A septum is formed which separates an end portion 
from the stalk. This end cell is the antheridium. Frequently!! 
is collapsed or empty as shown in fig. 10S. The protoplasm in 




Fig 10S. 
Vaucheria sessilis, one antheridium between two oogonia. 

the antheridium forms numerous small oval bodies each with two 
slender lashes, the cilia. When these are formed the antherid- 
ium opens at the end and they escape. It is after the escape 
of these spermatozoids that the antheridium is collapsed. Each 
spermatozoid is a male gamete. 

252. Oogonium. — The oogonia are short branches also, but 
they become large and II 

somewhat oval. T he { \ 

septum which separates the 
protoplasm from that of 
the main thread is as we 
see near the junction of 
the branch with the main 
thread. The oogonium, 
as shown in the figure, is 
usually turned somewhat 
to one side. When mature the pointed end opens and a bit of the 
protoplasm escapes. The remaining protoplasm forms the large 
rounded egg cell which fills the wall of the oogonium. In some 
of the oogonia which we examine this egg is surrounded by a 
thick brown wall, with starchy and oily contents. This is the 




Fig. 109. 
Vaucheria sessilis ; oogonium opening and emit- 
ting a hit of protoplasm; spermatozoids; sperma- 
tozoids entering oogonium. (After Pringsheim ami 
Goebel.) 



io8 



MORPHOLOG Y. 



fertilized egg (sometimes called here the oospore). It is freed 
from the oogonium by the disintegration of the latter, sinks into 




Fig. no. 
Fertilization in vaucheria. mn, male nucleus ; fn, female nucleus. Male nucleus entering 
the egg and approaching the female nucleus. (After Oltmans.) 

the mud, and remains here until the following autumn or spring, 
when it grows directly into a new plant. 

253. Fertilization. — Fertilization is accomplished by the 
spermatozoids swimming in at the open end of the oogonium, 






t'Y 



mm 



Fig. in. 
Fertilization of vaucheria. fn, female nucleus; mn, male nucleus. The different figures 
show various stages in the fusion of the nuclei. 

when one of them makes its way down into the egg and fuses 
with the nucleus of the egg. 

254. The twin vaucheria (V. geminata). — Another species of vaucheria 
is the twin vaucheria. This is also a common one, and may be used for 
study instead of the sessile vaucheria if the latter cannot be obtained. The 
sexual organs arc borne at the end of a club-shaped branch. There are 
usually two oogonia, and one antheridium between them which terminates 
the branch. In a closely related species, instead of the two oogonia there is 
a whorl of them with the antheridium in the center. 

255. Vaucheria compared with spirogyra. In vaucheria we have a plant 
which Is very interesting to compare with spirogyra in several respects. 



VAUCHEKIA. IO9 

Growth takes place, not in all parts <>l the thread, but Is localized at the ends 
of the thread and its branches. This represents a distinct advance on such 
a plant as spirogyra. Again, only specialized partsof the plant in vaucheria 
tonn the sexual organs. These are short branches. Farther there is a great 
difference in the size of the two organs, and especially in the size of the 
gametes, the supplying gametes (spermatozoids) being very minute, 
while the receptive gamete is large and contains all the nutriment for the 
fertilized egg. In spirogyra, on the other hand, there is usually no differ- 
ence in size of the gametes, as we have seen, and each contributes equally in 
the matter of nutriment for the fertilized egg. Vaucheria, therefore, rep- 
resents a distinct advance, not only in the vegetative condition of the plant, 
but in the specialization of the sexual organs. Vaucheria, with other related 
algae, belongs to a group known as the Siphonea, so called because the plants 
are tubedike or s/j)/wn-\ike. 



CHAPTER XVIII. 



COLEOCH^TE. 



256. Among the green algae coleochaete is one of the most 
interesting. Several species are known in this country. One 
of these at least should be examined if it is possible to obtain it. 
It occurs in the water of fresh lakes and ponds, attached to 
aquatic plants. 

257. The shield-shaped coleochaete. — This plant (C. scutata) 



frig. 112. 

Stem o f 
aquatic plant 
showing co- 
leu < hit c 

natural size. 




Fig. i 13 
Thallus of Coleochaete scutata. 



is in the form of a flattened, circular, green plate, as shown in 
fig. M2. It is attached near the center on one side to rushes 

no 



COLRQCIFA^TE. 



II I 



and other plants, and has been found quite abundantly for sev- 
eral years in the waters of Cayuga Lake at its southern extremity. 
As will be seen it consists of a single layer of green cells which 
radiate from the center in branched rows to the outside, the cells 
lying so close together as to form a continuous plate. The plant 
started its growth from a single cell at thecentral point, and grew 
at the margin in all directions. Sometimes they are quite irregu- 
lar in outline, when they lie quite closely side by side and inter- 
fere with one another by pressure. If the surface is examined 
carefully there will be found long hairs, the base of which is en- 
closed in a narrow sheath. It is from this character that the 
genus takes its name of coleochaete (sheathed hair). 

258. Fruiting stage of coleochsete. — It is possible at some 
seasons of the year to find rounded masses of cells situated near 
the margin of this green disk. These have developed from a 
fertilized egg which remained attached to the plant, and prob- 
ably by this time the parent plant has lost its color. 

259. Zoospore stage. — This mass of tissue does not develop 
directly into the circular green disk, but each of the cells forms 
a zoospore. Here then, as 
in cedogonium, we have an- 
other stage of the plant in- 
terpolated between the fer- 
tilized egg and that stage 
of the plant which bears the 
gametes. But in coleochaete 
we have a distinct advance in 
this stage upon what is pres- 
ent in cedogonium, for in ". Portion of tha Uusof Co- 

to leochaete scutata, showing 

coleochaete the fertilized "^p* .<*®* from whic , h 

zoogonicha have escaped, 

egg develops first into a °Vf. froni ** Vi 11 * z f°l °" 

oo 1 nidia at the left. (After 

several -celled mass of tissue Prmgsheim.) 

before the zoospores are formed, while in cedogonium only four 

zoospores are formed directly from the egg. 

260. Asexual reproduction. In asexual reproduction any of the green 
cells on the plant may form zoogonida. The content- of a cell round off and 





//T 

Fig. 1 15- 
Portion of thallus 
of Coleochaete 
scutata, showing 
four antheridia 
formed from one 
thallus cell : a sin- 
gle spermatozoid at 
the right. (After 
Pringsheim.) 



112 



MORPHOLOGY. 



form a single zoogonidium which has two cilia at the smaller end of the oval 
body, fig. 114. After swimming around for a time they come to rest, ger- 
minate, and produce another plant. 

261. Sexual reproduction. — Oogonium. — The oogonium is formed by the 
enlargement of a cell at the end of one of the threads, and then the end of the 



Oog--, 






Fig. 116. 

Coleochaete soluta ; at left branch bearing oogonium (oog) ; antheridia (ant); egg in 
oogonium and surrounded by enveloping threads ; at center three antheridia open, and one 
spermatozoid ; at right sporocarp, mature egg inside sporocarp wall. 

cell elongates into a slender tube which opens at the end to form a channel 

through which the spermatozoid may pass down to the egg. The egg is 

• formed of the contents of the cell (fig. 116). Several oogonia are formed on 

one plant, and in such a 

183? 



plant as C. scutata they are 
formed in a ring near the 
margin of the disk. 

262. Antheridia.- In C. 
scutata certain of the cells 
of the plant divide into four 
smaller cells, and each one 
of these becomes an antheri- 
lium. In C. soluta the an- 




Fig. 



Fig. 1 17 
Two sporocarps still 
surrounded by thallus. 
Thallus finally decays and 

sets sporocarp tree. 

Figs. 117, 1 1 s, ( '. scutata. 
times four in number or less (fig. 



iS. 



Sporocarp ruptured b y 
growth of egg to form cell theridia grow out from the 
mass. Cells of this sporo- . • 1 11 • 1 

phyte forming zoospores. end 01 terminal cells in the 

form of short flasks, some- 

16). A -ingle spermatozoid is formed 



from the contents. It is oval and potaesses two long cilia. Alter swim- 



COLEOCHJETE. I 13 

ming around it passes down the tube of the oogonium and fertilizes the 

263. Sporocarp. — Alter the egg is fertilized the ceils of the threads near 
the egg grow up around it and form a firm covering one cell in thickness. 
This envelope becomes brown and hard, and serves to protect theegg. This 
is the "fruit" of the coleochsete, and i> sometimes called a sporocarp 
(spore fruit). The development of the cell mass and the zoospores from the 
egg has been described above. 

Some of the species of coleochsete consist of branched threads, while others 
form circular cushions several layers in thickness. These form- together 
with the form of our plant C. scutata make an interesting series oi transi- 
tional forms from filamentous structures to an expanded plant body formed 
of a mass of cells. 



114 



MORPHOLOG Y. 



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CHAPTER XIX. 

BROWN AND RED ALG^E. 

265. If it is desired to extend the study of the algae to other groups, 
especially to some of the marine forms, examples of the brown algae and of 
the red algae may be obtained. These are accessible at the seashore, and 
for inland laboratories material may be preserved in formalin (2)4^)- 

266 The brown algae (Phaeophyceae).* — A good representative of one 
division of the brown algae and one often used for study is the genus fucus, 

267. Form and occurrence of fucus. — This plant is a more or less 
branched and flattened thallus or " frond." One of them, illustrated in fig. 
119, measures 15-30*7/3 (6-12 inches) in length. It is attached to rocks 
and stones which are more or less exposed at low tide. From the base of the 
plant are developed several short and more or less branched expansions 
called ••holdfasts," which, as their name implies, are organs of attachment. 
Some species (F. vesiculosus) have vesicular swellings in the thallus. 

The fruiting portions are somewhat thickened as shown in the figure. 
Within these portions are numerous oval cavities opening by a circular pore, 
which gives a punctate appearance to these fruiting cushions. Tufts of hairs 
frequently project through them. 

268. Structure of the conceptacles. — On making sections of the fruiting 
portions one finds the walls of the cavities covered with outgrowths. Some 
of these are short branches which bear a large rounded terminal sac, the 
oogonium, at maturity containing eight egg cells. More slender and much 
branched threads bear narrowly oval antheridia. In these are developed 
several two-ciliated spermatozoids. 

269. Fertilization. — At maturity the spermatozoids and egg cells float out- 
side of the oval cavities where fertilization takes place. The spermatozoid 
sinks into the protoplasm of the egg cell, makes its way to the nucleus oi 
the egg. and fuses with it as shown in fig. 125. The fertilized egg then 
grows into a new plant. Nearly all the brown algae are marine. 

* The members of the group possess chlorophyll, but it 1- obscured by a 
brown pigment. 

115 



i6 



MORPHOLOGY. 



270. The red algae (Rhodophyceae). — The larger number of the so-called 
red algae occur in salt water, though a few genera occur in fresh water. 




Fig. ii 9 . 
Portion of plant of fucus showing 
conceptacles in enlarged ends ; and 
below the vesicles (Fucus vescicu- 
losus). 



Fig. 120. 
Section of conceptacle of fucus, showing 
oogonia, and tufts of antheridia. 



(Lemanea grows only in winter in turbulent water of quite large streams. 
Batrachospermum grows in rather slow-running water of smaller streams. 
Both of these inhabit fresh water.) The plants of the group possess chloro- 
phyll, but it is usually obscured by a reddish or purple pigment. 

271. Gracillaria — Gracillaria is one of the marine forms, and one species 
i^ illustrated in fig. 126. It measures \^~20t))i or more long, and is pro- 
fusely branched in a palmate manner. The parts of the thallus are more or 
less flattened. The fruit is a cystocarp, which is characteristic of the rhodo- 



BROWN .IX J) RED ALGAi. 



117 



phyccee (floridcae). In gracillaria these fruit bodies occur scattered over 
the thallus. They are somewhat flask-shaped, are partly sunk in the 




Fig. 122. 
Antheridia of fucus, 
branched threads. 



Fig. 123. Fig. 124. 

on Antheridia of fucus with Egg of fucus surrounded 
escaping spermatozoids. by spermatozoids. 



thallus, and the conical end projects strongly above the surface. The car- 
pospores are grouped in radiating threads within the oval c vity of the 








Fig. 125. 
Fertilization in fucus ; fn, female nucleus ; ;//;/, male nucleus; ?/, nucleolus. In the left 
figure the male nucleus is shown moving down through the cytoplasm of the egg ; in the 
remaining figures the cytoplasm of the egg is omitted. (After Strasburger.) 



cystocarp. These cystocarps are developed as a result of fertilization. 
Other plants bear gonidia in groups of four, the so-called tetraspores. 

272. Rhabdonia. — This plant is about the same size as the gracillaria, 
though it possesses more filiform branches. The cystocarps form prominent 
elevations, while the carpospores Lie in separated groups around tin periph- 
ery of a sterile tissue within the cavity. (Sec figs. 128, 129.) Gonidia in 
the form of tetraspores are also developed in rhabdonia. 



u8 



MORPHOLOG Y. 




Fig. 126. Fig. 127. 

Gracillaria, portion of frond, Gracillaria, section of cystocarp 

showing position of cysto- showing spores, 
carps. 



273. The principal groups of the algae are the following : 



Chlorophycece. 
Green algae. 



Protococcoideae (the protococcus (Pleurococ- 

cus vulgaris); the red -snow plant (Sphaerella 

nivalis), etc. 
Conjugateae (spirogyra, zygnema, mougeotia, 

desmids, etc.). 
Siphoneae (vaucheria). 
Confervoideae (oedogonium, chaetophora, cole- 

ochaete). 



CyanophycecB (nostoc, oscillatoria, etc.). The blue-green algae. 
Phceophycem (fucus, etc.). The brown algae. 



BROWN AND RED ALGAl. 



II 9 



Rhodophyceie (rhabdonia, gracillaria, callithamnion, champia, 

etc.). The red alga:. 

274. Some of the protococcoidese arc believed to lie very near 

some of the lower animals like the flagellates. They are mostly 
single-celled plants ; some of them arc 
motile during the vegetative stage, and 
others are not motile, while others are 




Fig. 128, 

Rhabdonia, branched 
portion of frond show- 
ing cystocarps. 




Fig. 129. 

Section of cystocarp of rhabdonia, showing 
spores. 



motile during certain stages. The red-snow plant 
may be obtained by scraping the red-looking 
matter out of the bottom of dry shallow basins in 
the rocks, close by fresh-water streams or lakes. 
By placing some of this material in a vessel of 
water for a few days the motile stage may be Flg - I3 °- 

Pleurococcus (pro- 

obtained. The protococcus, or Pleurococcus vul- tococcus) vulgaris. 

garis, may be obtained on the north side of trees, rocks, and 
walls, in damp places. 




CHAPTER XX. 

FUNGI : MUCOR AND SAPROLEGNIA. 

Mucor. 

275. In the chapter on growth, and in our study of proto- 
plasm, we have become familiar with the vegetative condition of 
mucor. We now wish to learn how the plant multiplies and re- 
produces itself. For this study we may take one of the mucors. 
Any one of several species will answer. This plant may be grown 
by placing partially decayed fruits, lemons, or oranges, from which 
the greater part of the juice has been removed, in a moist cham- 
ber ; or often it occurs on animal excrement when placed under 
similar conditions. In growing the mucor in this way we are 
likely to obtain Mucor mucedo, or another plant sometimes 
known as Mucor stolon ifer, or Rhizopus nigricans, which is illus- 
trated in fig. 132. This latter one is sometimes very injurious to 
stored fruits or vegetables, especially sweet potatoes or rutaba- 
gas. Fig. 131 is from a photograph of this fungus on a banana. 

276. Asexual reproduction. — On the decaying surface of the 
vegetable matter where the mucor is growing there will be seen 
numerous small rounded bodies borne on very slender stalks. 
These heads contain the gonidia, and if we sow some of them in 
nutrient gelatine or agar in a Petrie dish the material can be 
taken out very readily for examination under the microscope. 
Or we may place glass slips close to the growing fungus in the 
moist, chamber, so that the fungus will develop on them, though 
cultures in a nutrient medium are much better. Or we may take 
the material directly from the substance on which it is growing. 

120 



FUNGI: Mr CO A'. 



121 



After mounting a small quantity of the mycelium bearing these 

heads, if we have been careful to take it where the heads appear 
quite young, it may be possible to study the early stages of their 




Fig. 131. 
Portion of banana with a mould (Rhizopus nigricans) growing on one end. 

development. We will probably note at once that the stalks or 
upright threads which support the heads are stouter than the 
threads of the mycelium. 

These upright threads soon have formed near the end a cross 
wall which separates the protoplasm in the end from the remain- 
der. This end cell now enlarges into a vesicle of considerable 
size, the head as it appears, but to which is applied the name of 
sporangium (sometimes called gonidangium), because it encloses 
the gonidia. 

At the same time that this end cell is enlarging the cross wall 
is arching up into the interior. This forms the columella. All 
the protoplasm in the sporangium now divides into gonidia. 
These arc small rounded or oval bodies. The wall of the spo- 



122 



MORPHOLOGY. 



rangium becomes dissolved, except a small collar around the 
stalk which remains attached below the columella (fig. 133). 




Fig. 132. 

Group of sporangia of a mucor (Rhizopus nigricans) showing rhizoids and the stolon extend- 
ing from an older group. 

By this means the gonidia are freed. These gonidia germinate 
and produce the mycelium again. 

277. Sexual stage. — This stage is not so frequently found, but may some- 
times be obtained by growing the fungus on bread. 

Conjugation takes place in this way. Two threads of the mycelium which 
lie near each other put out each a short branch which is clavate in form. 
The ends of these branches meet, and in each a septum is formed which cuts 
off a portion of the protoplasm in the end from that of the rest of the my- 
celium. The meeting walls of the branches now dissolve and the protoplasm 
of each gamete fuses into one mass. A thick wall is now formed around this 
mass, and the outer layer becomes rough and brown. This i- the zygote ox 
zygospore. The mycelium dies and it becomes free often with the suspensors, 
as the stalks ot these sexual brandies are called, still attached. This zygo- 
spore passes through a period of rest, when with the entrance of favorable 
conditions of growth it germinates, and usually produces directly a sporan- 
gium with gonidia. This completes the normal lite cycle of the plant. 

278. Gemmae.- Gemmae, as they are sometimes called, are often formed 01 

the mycelium. A short cell with a stout wall is formed on the side of ; 



FUNGI : S. 1 PROLEGNIA. 



123 



thread of the mycelium. In other cases large portions of the threads of the 
mycelium may separate into chains of cells. Both these kinds of cells are 





Fig. 133- 
A mucor (Rhizopns nigricans) ; at left nearly mature sporangium with columella showing 
within; m the middle is ruptured sporangium with some of the gonidia clinging to the colu- 
mella ; at right two ruptured sporangia with everted columella. 



capable of growing and forming 
called chlamy do spores. 



the mycelium again. They are sometimes 



Water Moulds (Saprolegnia). 

279. The water moulds are very interesting plants to study 
because they are so easy to obtain, and it is so easy to observe a 
type of gonidium here to which we have referred in our studies 
ofthealgae, the motile gonidium, or zoogonidium. (See appen- 
dix for directions for cultivating this mould.) 

280. Appearance of the saprolegnia. — In the course of a 
few days we are quite certain to see in some of the cultures deli- 
cate whitish threads, radiating outward from the bod) 01 the tl\ 
in the water. A few threads should be examined from day to 
day to determine the stage of the fungus. 

281. Sporangia of saprolegnia. — The sporangia of saprolegnia 
can be easily detected because they are much stouter than the 



124 



MORPHOLOGY. 



ordinary threads of the mycelium. Some of the threads should 
be mounted in fresh water. Search for some of those which 




Fig. 134- 
Sporangia of saprolegnia, one showing the escape of the 
nidia. 



zoogo- 



show that the protoplasm is divided up into a great number of 
small areas, as shown in fig. 134. 

With the low power we should watch some of the older ap- 
pearing ones, and if after a few minutes they do not open, other 
preparations should be made. 

282. Zoogonidia of saprolegnia. — The sporangium opens at 








Fig. 135- 
Branch of saprolegnia showing oogonia with oospores, eggs matured parthenogenetically. 

the end, and the zoogonidia swirl out and swim around for a 
short time, when they come to rest. With a good magnifying 






Fl 'NG1 : S. 1 /'A'( U.ECNIA. 



125 





Fig. 136. 
Fertilization in saprolegnia, tube of antheridium carrying m the nucleus of the sperm cell 
to the egg. In the right-hand figure a smaller sperm nucleus is about to fuse with the 
nucleus of the egg. (After Humphrey and Trow.) 





Fig- i37. 
Branching hypha of Peronospora alsinearum. 



Fig. 138. 
Branched hypha of downy mildew 
of grape showing peculiar branching 
(Plasmopara viticola). 



126 



MORPHOLOG Y. 



power the two cilia on the end may be seen, or we may make 
them more distinct by treatment with Schultz's solution, draw- 
ing some under the cover glass. The zoogonidium is oval and 
the cilia are at the pointed end. After they have been at rest 




Fig. i39- 
Downy mildew of grape (Plasmopora viti- 
cola), showing tuft of gonidiophores bearing 
gonidia, also intercellular mycelium. (After 
Millardet.) 



Fig. 140. 
Phytophthora infestans showing pe- 
culiar branches; gonidia below. 



for some time they often slip out of the thin wall, and swim 
again, this time with the two cilia on the side, and then the 
zoogonidium is this time more or less bean-shaped or reniform. 

283 Sexual reproduction of saprolegnia. — When such cultures are older 
we often see large rounded bodies either at the end of a thread, or of a 

branch, which contain several smaller rounded bodies as shown in fig. 135. 
These are the oogonia (unless the plant is attacked by a parasite), and the 
round bodies inside are the egg cells, it before fertilization, or the ee^s, if 



FUNGI: SAPROl.ECNIA. 



127 



after this process lias taken place. Sometimes the slender antheridium can 

be -ecu coiled partly around the oogonium, and one end entering to come in 
contact with the egg cell. But in some species the antheridium i- not 
present, and that is the case with the species figured .it 135. In this case 




Fig. 141. Fig. 142. 

Gonidiophores and gonidia of potato blight (Phytophthora in- Gonidia of potato 

festans). />, an older stage showing how the branch enlarges where blight forming zoogo- 

it grows beyond the older gonidium. (After de Bary.) nidia. v After de Bary.) 

the eggs mature without fertilization. This maturity of the egg without 
fertilization is ttlledjfartfcnogenesis, which occurs in other plants also, but 
is a rather rare phenomenon. 

284. In fig. 136 is shown the oogonium and an antheridium, and the 
antheridium is carrying in the male nucleus to the e^g cell. Spermatozoids 



ypfek. 










?-=*••: 



mi 
i \ I! 



* 



Fig. 14.S • 
Fertilization in Peronospora alsinearum ; tube from antheridium carrying in the sperm 
nucleus in figure at the left, female nucleus near; fusion of the two nuclei shown in the two 
other figures. (After Berlese.) 

are not developed here, but a nucleus in the antheridium reaches the v^ir 
cell. It sinks in the protoplasm of the egg, comes in contact with tla- nu- 
cleus of the egg, and fuses with it. Thus fertilization is accomplished. 



128 



MORPHOLOGY. 



Downy Mildews. 

285. The downy mildews make up a group of plants which are closely 
related to the water moulds, but they are parasitic on land plants, and some 
species produce very serious diseases. The mycelium grows between the 
cells of the leaves, stems, etc., of their hosts, and sends haustoria into the 
cells to take up nutriment. Gonidia are formed on threads which grow 
through the stomates to the outside and branch as shown in tigs. 137-140. 

The gonidia are borne on the tips 
of the branches. The kind of 
branching bears some relation to 
the different genera. Fig. 137 is 
from Peronospora alsinearum on 
leaves of cerastium; figs. 138 
and 139 are Plasmopara viticola, 
the grape mildew, while figs. 140 
and 141 are from Phytophthora 
infestans, which causes a disease 
known as potato blight. The 
gonidia of peronospora germinate 
by a germ tube, those of plasmop- 
ara first form zoogonidia, while 
in phytophthora the gonidium 
may either germinate forming a 
thread, or each gonidium may 
first form several zoogonidia as shown in fig. 142. 

286. In sexual reproduction oogonia and antheridia are developed on the 
mycelium within the tissues. Fig. 143 represents the antheridium entering 
theoogoniunij and the male nucleus fusing with the female nucleus in fertili- 
zation. The sexual organs of Phytophthora infestans are not known. 

287. Minor, saprolegnia, peronospora, and their relatives have few or 
no septa in the mycelium. In this respect they resemble certain of the algae 
like vaucheria, but they lack chlorophyll. They are sometimes called the 
alga-like fungi and belong to a large group called Phycomycetes. 




Fig 144. 
Ripe oospore of Peronospora alsinearun 



CHAPTER XXI. 



FUNGI CONTINUED (RUSTS AND SAC FUNGI). 



"Rusts" (Uredineae). 

288. The fungi known as " rusts " are very important ones 
to study, since all the species are parasitic, and many produce 
serious injuries to crops. 

289. Wheat rust (Puccinia graminis). — The wheat rust is 
one of the best known of these fungi, since a great deal of study 
has been given to it. One form of the plant occurs in long 






I 



Fig- i45« 


Fig. 146. 


Fig. 147. 


Fig. 148. 


Fig. 149. 


Wheat leaf with red 


Portion of leaf 


Natural size. 


Enlarged. 


S ingle 


rust, natural size. 


enlarged to show 






sorus. 



Figs. 145, 146. — Puccinia graminis, red-rust stage (uredo stage). 
Figs. 147-149. — Black rust of wheat, showing sori of teleutospores. 

reddish-brown or reddish pustules, and is known as the " red 
rust" (figs. 145, 1 46 ). Another form occurs in elongated black 
pustules, and this form is the one known as the, "black rust" 

129 



130 



MORPHOLOGY. 



(figs. 147-150). These two forms occur on the stems, blades, 
etc., of the wheat, also on oats, rye, and some of the grasses. 

290. Teleutospores of the black-rust form. — If we scrape off 
some portion of one of the black pustules (sori), tease it out 




Fig. 150. 
Head of wheat showing black rust spots 
on the chaff and awns. 




Fig. 151. 
Teleutospores of wheat rust, 
showing two cells and the pedicel. 




Fig. 152. 
Uredospores of wheat rust, one 
showing remnants of the pedicel. 



in water on a slide, and examine with a microscope, we will see 
numerous gonidia, composed of two cells, and having thick, 
brownish walls as shown in fig. 151. Usually there is a slender 
brownish stalk on one end. These gonidia are called teleuto- 
spores. They are somewhat oblong or elliptical, a little con- 
stricted where the septum separates the two cells, and the end 
cell varies from ovate to rounded. The mycelium of the fungus 






FUNGI: RUSTS. 



13* 



courses between the cells, just as is found in the case ol the 
carnation rust, which belongs to the same family (see Tart III). 
291. Uredospores of the red-rust form. — If we make a simi- 
lar preparation from the pustules of the red-rust form we will see 
that instead of two-celled gonidia they are one-celled. The 
walls are thinner and not so dark in color, and the) are covered 
with minute spines. They have also short stalks, but these fall 
away very easily. These one-celled gonidia of the red-rust form 
are called " uredospores." The uredospores and teleutospores 
are sometimes found in the same pustule. 

It w r as once supposed that these two kinds of gonidia belonged 
to different plants, but now it is known that the one-celled 
form, the uredospores, is a form developed 
earlier in the season than the teleutospores. 
292. Cluster-cup form on the barberry. 
— On the barberry is found still another 
form of the wheat rust, the " cluster cap" 
stage. The pustules on the under side of 
the barberry leaf are cup-shaped, the cups 
being partly sunk in the tissue of the leaf, 
while the rim is more or less curved back- 
ward against 
the leaf, and 
split at several 
places. These 
cups occur in 
clusters on the 
affected spots 
of the barberry 
leaf as shown 

tig- i54- * M g- J 55- 

Single spot Two cluster in fig. 1 54. 

showing cluster cups more en- 

cups enlarged, larged, showing Within the 

split margin. 

Figs. 153-155. — Cluster-cup stage of wheat rust. CUpS lUimbelS 

of one-celled gonidia (orange in color, called aecidi os pores I are 
borne in chains from short branches ot the mycelium, which 
fill the base of the cup. In fact the wall of the cup (peridium) 






tig. 153. 
Barberry leaf with two 
diseased spots, natural 
size. 



132 



MOKPHOLOG V. 



is formed of similar rows of cells, which, instead of separating 
into gonidia, remain united to form a wall. These cups are 
usually borne on the under side of the leaf. 

293. Spermagonia. — Upon the upper side of the leaves in the same spot 
occur small, orange -colored pustules which are flask-shaped. They bear 
inside, minute, rod-like bodies on the ends of slender threads, which ooze 




Fig. 156. 
Section of an aecidium (cluster cup) from barberry leaf. (After Marshall-Ward.) 



out on the surface of the leaf. These flask-shaped pustules are called 
spermagonia, and the minute bodies within them spermatid, since they were 
once supposed to be the male element of the fungus. Their function is not 
known. They appear in the spots at an earlier time than the cluster cups. 

293a. How the cluster-cup stage was found to be a part of the wheat rust. 
— The cluster-cup stage of the wheat rust was once supposed also to be a dif- 
ferent plant, and the genus was called cecidium. The occurrence of wheat 
rust in great abundance on the leeward side of affected barberry bushes in 
England suggested to the fanners that wheat rust was caused by barberry 
rust. It was later found that the secidiospores of the barberry, when sown 
on wheat, germinate and the thread of mycelium enters the tissues of the 
wheat, forming mycelium between the cells. This mycelium then bears 
the uredospores, and later the teleutospores. 






FUNGI: RUSTS. 



•33 



294. Uredospores can produce successive crops of uredospores. — The uredo- 
spores are carried by the wind to other wheat or grass plants, germinate, 




Fig. 157. 

Section through leaf of barberry at point affected with the cluster-cup stage of the wheat 
rust; spermagonia above, aecidia below. (After Marshall-Ward.) 

form mycelium in the tissues, and later the pustules with a second crop of 
uredospores. Several successive crops of uredospores may be developed in 





Fig. 158. 
^.section through sorus of black rust of wheat, showing teleutospores. />, mycelium 
bearing both teleutospores and uredospores. < Alter de Bary.) 

one season, so this is the form in which the fungus is greatly multiplied and 

widely distributed. 



134 



MORPHOLOGY. 



295. Teleutcspores the last stage of the fungus in the season. — The teleu- 
tospores are developed late in the season, or late in the development of the 

host plant (in this case the 
wheat is the host). They 
' then rest during the winter. 
In the spring under favor- 
able conditions each cell of 
the teleutospore germi- 
nates, producing a short 
mycelium called a promy- 
celium, as shown in figs. 
161, 162. This promy- 
celium is usually divided 
into four cells. From each 
cell a short, pointed pro- 
cess is formed called a 
" sterigma." Through this 
the protoplasm moves and 
forms a small gonidium on 
the end, sometimes called 
a sporidiiun. 

296. How the fungus gets from the wheat back to the barberry. — If these 
sporidia from the teleutospores are carried by the wind so that they lodge on 




Fig. 160. 

Germinating uredospore of Germ tube entering the 

wheat rust. (After Marshall- leaf through a stoma. 
Ward.) 




1 eleutospore 
tiating, forming 
celium. 



'i. Fig. 162. Ffg. 163. 

germi- Promycelium of ger- Germinating sporidia entering leaf 

pro my- minating teleutospore, of barberry by mycelium, 
forming sporidia. 



Figs. 161-163. — Puccinia graminis (wheat rust). (Alter Marshall-Ward.) 



FUNGI: RUSTS. 135 

the leaves of the barberry, they germinate and produce the cluster cup again. 
The plant has thus a very complex life history. Because of the presence oi 
several different forms in the lite cyle, it is called a polymorphic fungus. 

The presence of the barberry does not seem necessary in all cases for the 
development of the fungus from one year to another. 

297. Synopsis of life history of wheat rust. 
Cluster-cup stage on leaf of barberry . 

Mycelium between cells of leaf in affected spots. 
Spermagonia (sing, spermagonium), small flask-shaped bodies 

sunk in upper side of leaf; contain " spermatia." 
JEcidia (sing, aecidium), cup-shaped bodies in under side of 
leaf. 
Wall or peridium, made up of outer layer of fungus threads 

which are divided into short cells but remain united. 
At maturity bursts through epidermis of leaf; margin of 
cup curves outward and downward toward surface of leaf. 
Central threads of the bundle are closely packed, but free. 
Threads divide into short angular cells which separate 
and become secidiospores, with orange-colored content. 
T^Ecidiospores carried by the wind to wheat, oats, grasses, 
etc. Here they germinate, mycelium enters at stomate, 
and forms mycelium between cells of the host. 

Credo s/age {red rust) on wheat, oats, grasses, etc. 
Mycelium between cells of host. 
Bears uredospores (i -celled) in masses under epidermis, which 

is later ruptured and uredospores set free. 
Uredospores carried by wind to other individual hosts, and 

new crops of uredospores formed. 

Teleutospore stage [black rust), also on wheat, etc. 
Mycelium between cells of host. 
Bears teleutospores (2-celled) in masses (sori) under epidermis, 

• which is later ruptured. 
Teleutospores rest during winter. In spring each cell germi- 
nates and produces a promyc^ium, a short thread, divided 
into four cells. 



I36 MORPHOLOGY, 

Promycelium bears four sterigmata and four gonidia (or spo- 
ridia), which in favorable conditions pass back to the bar- 
berry, germinate, the tube enters between cells into the 
intercellular spaces of the host to produce the cluster cup 
again, and thus the life cycle is completed. 

298. Higher fungi divided into two series. — Of the higher fungi there 
are two large series. One of these is represented by the mushrooms, a good 
example of which is the common mushroom (Agaricus campestris). 
(For the study of the mushrooms see Part III, Ecology.) 
The large group of fungi to which the mushroom belongs is called the 
basidio)nycetes because in ail of them a structure resembling a club, or basid- 
ium, is present, and bears a limited number of spores, usually four, though 
in some genera the number is variable. Some place the rusts (uredinece) in 
the same series (basidium series) because of the short promycelium, and 
four sporidia developed from each cell of the teleutospore. 

Sac Fungi. 

299. The other large series of the higher fungi may be rep- 
resented by what are popularly called the "powdery mildews." 
Fig. 164 is from a photograph of two willow leaves affected by 
one of these mildews. The leaves are first partly covered with a 
whitish growth of mycelium, and numerous chains of colorless 
gonidia are borne on short erect threads. The masses of gonidia 
give the leaf a powdery appearance. The mycelium lives on the 
outer surface of the leaf, but sends short haustoria into the epi- 
dermal cells. 

300. Fruit bodies of the willow mildew. — On this same 
mycelium there appear later numerous black specks scattered 
over the affected places of the leaf. These are the fruit bodies 
[perithecia). If we scrape some of these from the leaf, and 
mount them in water for microscopic examination, we shall be 
able to see their structure. Examining these first with a low 
power of the microscope, each one is seen to be a rounded body, 
from which radiate numerous filaments, the appendages, Each 
one of these appendages iscoiled at the end into the form of a 
little hook. Because of these hooked appendages this genus is 
called uncinula. This rounded body is the perithecium* 



FUNGI: SAC FUNGI 



137 



301. Asci and ascospores. — While we arc looking at a few of 
these through the microscope with the low power, we should 




Fig. 164. 

Leaves of willow showing willow mildew. The black dots are the fruit bodies (perithecia) 

seated on the white mycelium. 

press on the cover glass with a needle until we see a few of the 
perithecia rupture. If this is done carefully we will see several 
small ovate sacs issue, each containing a number of spores, as 
shown in fig. 166. Such a sac is an ascus, and the spores are 
ascospores. 






138 



MORPHOLOG Y. 



302. The sac fungi or ascomycetes. — The large group of fungi to which 
this uncinula belongs is known as the sac fungi, or ascomycetes. While 







Fig. 165. 
Willow mildew; bit 
of mycelium with 
erect conidiophores, 
bearing chain of 
gonidia ; gonidium at 
left germinating. 



Fi S- l66 - Fig. 167. 

Fruit of willow mildew, showing hooked ap- Fruit body of an- 

pendages. Genus uncinula. other m iiaew with 

Figs. 166, 167. — Perithecia (perithecium) of dichotomousappen- 

two powdery mildews, showing escape of asci dages. Genus 

containing the spores from the crushed fruit microsphaera. 
bodies. 



many of the powdery mildews have a variable number of spores in an ascus, 
a large majority of the ascomycetes have just 8 spores in an ascus, while 





Fig. 168. 
Contact of an- 
theridium and 
carpo gon ium 
(carpogonium 
the larger cell); 
the beginning 
of fertilization. 



Fig, 169. 

D i s a p p e a r- 

ance of contact 
walls of anthe- 
r i d i u m and 
carpogo ni 11111, 
and fusion of 
the two nuclei. 




Fig. 170. 
Fertilized egg surrounded by 
the enveloping threads which 
grow up around it. 



Figs. 168-170.— Fertilization m spluerotheca ; one of the powdery mildews. (After Harper.) 

some have 4, others 16, and some an indefinite number. The complex struc- 
ture of the fruit body, as well as the usually definite and limited number of 



Fl '. V6V ; i V. .1 SS1FICA TION. 



139 



spores in an ascus, places these fungi on a higher scale than the mucors, 
saprolegnias, and their relativeSj where the number of gonidia in a sporangium 
is always indefinite. 

303. Leaf curl of the peach, black knot of the plum and cherry, ergot of 
the rye and grasses, and many other fungi are members of the ascomycetes. 
The majority of the lichens are ascomycetes, while a few arc basidiomycetes. 

304. Classification of the fungi.— Those who believe tli.it the fungi repre- 
sent a natural group of plants arrange them in three large series related to 
each other somewhat as follows: 



The Gonidium Type or Series. The 
number of gonidia in the sporangium 
is indefinite and variable. It may be 
very large or very small, or even only 
one in a sporangium. To this series 
belong the lower fungi; ex., mucor, 
^aprolegnia, peronospora, etc. 



The Basidium Type or Series. 

The number of gonidia on a basi- 
dium is limited and definite, and 
the basidium is a eharaeteristic 
structure; ex. uredineae (rusts), 
mushrooms, etc. 

The Ascus Type or Series. The 
number of spores in an ascus is 
limited and definite, and the ascus 
is a characteristic structure; ex. 
leaf curl of peach (exoascus), pow- 
dery mildews, black knot of plum, 
black rot of grapes, etc. 



305. Others believe that the fungi do not represent a natural group, but 
that they have developed off from different groups of the algae by becoming 
parasitic. As parasites they no longer needed chlorophyll, and consequently 
lost it. They thus derive their carbohydrates from organic material manu- 
factured by the green plants. 

According to this view the lower fungi have developed off from the lower 
algae (saprolegnias. mucors, peronosporas, etc., being developed off from 
siphonaceons algae like vaucheria), and the higher fungi being developed off 
from the higher algae (the ascomycetes perhaps from the rhodophyceae). 



CHAPTER XXII. 

LIVERWORTS (HEPATIC^). 

306. We come now to the study of representatives of another 
group of plants, a few of which we examined in studying the organs 
of assimilation and nutrition. I refer to what are called the liver- 
worts. Two of these liverworts belonging to the genus riccia 
are illustrated in figs. 58, 171. 

Riccia. 

307. Form of the floating riccia (R. fluitans). — The gen- 
eral form of floating riccia is that of a narrow, irregular, flattened, 
ribbon-like object, which forks repeatedly, in a dichotomous 
manner, so that there are several lobes to a single plant. It 
receives its name from the fact that at certain seasons of the year 
it may be found floating on the water of pools or lakes. When 
the water lowers it comes to rest on the damp soil, and rhizoids 
are developed from the under side. Now the sexual organs, and 
later the fruit capsule, are developed. 

308. Form of the circular riccia (R. crystallina). — The 
circular riccia is shown in fig. 171. The form of this one is quite 
different from the floating one, but the manner of growth is much 
the same. The branching is more compact and even, so that a cir- 
cular plant is the result. This riccia inhabits muddy banks, 
lying flat on the wet surface, and deriving its soluble food by 
means of the little rootlets (rhizoids) which grow out from the 
under surface. 

Here and there on the margin are narrow slits, which extend 

140 



L 1 1 'ER WO R 'J 'S : RICCIA. 



141 




Fig. 171. 

Thallus of Riccia crystallina. 



nearly to the central point. They are not real slits, however, for 
they were formed there as the plant grew, Each one of these 
V-shaped portions of the thal- 
lus is a lobe, and they were 
formed in the young condition 
of the plant by a branching 
in a forked manner. Since 
growth took place in all direc- 
tions radially the plant be- 
came circular in form. These 
large lobes we can see are 
forked once or twice again, 
as shown by the seeming- 
shorter slits in the margin. 

309. Sexual organs. — In 
order to study the sexual organs we must make thin sections 
through one of these lobes lengthwise and perpendicular to the 
thallus surface. These sections are mounted for examination 
with the microscope. 

310. Archegonia. — We are apt to find the organs in various stages of de- 
velopment, but we will select one of the flask-shaped structures shown in fig. 
172 for study. This flask-shaped body we see is entirely sunk in the tissue 
of the thallus. This structure is the female organ, and is what we term in 
these plants the archegonium. It is more complicated in structure than the 
oogonium. The lower portion is enlarged and bellied out, and is the venter 
of the archegonium, while the narrow portion is the neck. ■ We here see it in 
section. The wall is one cell layer in thickness. In the neck is a canal, 
and in the base of the venter we see a large rounded cell with a distinct 
and large nucleus. This cell is the egg cell. 

311. Antheridia. — The antheridia are also borne in cavities sunk in the 
tissue of the thallus. There is here no illustration of the antheridium of this 
riccia, but fig. 178 represents an antheridium of another liverwort, and there 
is not a great difference between the two kinds. Each one of those little rect- 
angular sperm mother cells in the antheridium changes into a swiftly moving 
body like a little club with two long lashes attached to the smaller end By 
the violent lashing of these organs the spermatozoid is moved through thewater, 
or moisture which is on the surface of the thallus. It moves through the canal 
of the archegonium neck and into the egg. where it fuses with the nucleus of 
the ^g, and thus fertilization is effected. 



142 



MORPHOLOGY. 



312. Embryo. — In the plants which we have selected thus far for study, 
the egg, immediately after fecundation, we recollect, passed into a resting 
state, and was enclosed by a thick protecting wall. But in riccia, and in the 
other plants of the group which we are now studying, this is not the case. 





Fig. 172. 
Archegonium of riccia, showing neck, 
venter, and the egg; archegonium is partly- 
surrounded by the tissue of the thallus. 
(Riccia crystallina.) 



Fig. 173- 
Young embryo (sporogoni- 
um) of riccia, within the venter 
of the archegonium ; the latter 
has now two layers of cells. 
(Riccia crystallina.J 



The egg, on the other hand, after acquiring a thin wall, swells up and fills 
the cavity of the venter. Then it divides by a cross wall into two cells. 
These two grow, and divide again, and so on until there is formed a quite 
large mass of cells rounded in form and still contained in the venter of the 
archegonium, which itself increases in size by the growth of the cells of the 
wall. 

313. Sporogonium of riccia. — The fruit of riccia, which is 
developed from the fertilized egg in the archegonium, forms a 
rounded capsule still enclosed in the venter of the archegonium, 
which grows also to provide space for it. Therefore a section 
through the plant at this time, as described for the study 
of the archegonium, should show this capsule. The capsule 
then is a rounded mass of cells developed from the egg. A sin- 
gle outer layer of cells forms the wall, and therefore is sterile. 



LIVERWORTS: RTCCIA: 



143 



AH the inner cells, which are richer in protoplasm, divide into 
four cells each. Each of these cells becomes a spore with a thick 
wall, and is shaped like a triangular pyramid whose sides are of 
the same extent as the base (tetrahedral). These cells formed in 






Fig. 174. 
Nearly mature sporogonium of Riccia crystallina ; 



Fig. 175- 
Riccia glauca ; archegonium 
containing nearly mature spo- 
rogonium. sg\ spore-producing 
cells surrounded by single layer 
of sterile cells, the wall of the 
sporogonium. 



mature spore at the right 

fours are the spores. At this time the wall of the spore-case dis- 
solves, the spores separate from each other and fill the now en- 
larged venter of the archegonium. When the thallus dies they 
are liberated, or escape between the loosely arranged cells of 
the upper surface. 

314. A new phase in plant life. — Thus we have here in the 
sporogonium of riccia a very interesting phase of plant life, in 
which the egg, after fertilization, instead of developing directly 
into the same phase of the plant on which it was formed, 
grows into a quite new phase, the sole function of which is the 
development of spores. Since the form of the plant on which the 
sexual organs are developed is called the gametophyte^ this new 
phase in which the spores are developed is termed the sporo- 
phyie. 

Now the spores, when they germinate, develop the gameto- 
phyte, or thallus, again. So we have this very interesting condi- 



144 MORPHOLOGY. 

tion of things, the thallus (gametophyte) bears the sexual organs 
and the unfertilized egg. The fertilized egg, starting as it does 
from a single-celled stage, develops the sporogonium (sporo- 
phyte). Here the single-cell stage is again reached in the spore, 
which now develops the thallus. 

315. Riccia compared with coleochaete, cedogonium, etc. — We have said 
that in the sporogonium of riccia we have formed a new phase in plant life. 
If we recur to our study of coleochaete we may see that there is here possibly 
a state of things which presages, as we say, this new phase which is so well 
formed in riccia. We recollect that after the fertilized egg passed the period 
of rest it formed a small rounded mass of cells, each of which now forms a 
zoospore. The zoospore in turn develops the normal thallus (gametophyte) 
of the coleochaete again. In coleochaete then we have two phases of the 
plant, each having its origin in a one-celled stage. Then if we go back to 
cedogonium, we will remember that the fertilized egg, before it developed 
into the cedogonium plant again (which is the gametophyte), at first divides 
into four cells which become zoospores. These then develop the cedogonium 
plant. 

Note. Too much importance should not be attached to this seeming ho- 
mology of the sporophyte of cedogonium, coleochaete, and riccia, for the nu- 
clear phenomena in the formation of the zoospores of cedogonium and coleo- 
chaete are not known. They form, however, a very suggestive series. 



Marchantia. 

316. The marchantia (M. polymorpha) has been chosen for 
study because it is such a common and easily obtained plant, and 
also for the reason that with comparative case all stages of 
development can be obtained. It illustrates also very well cer- 
tain features of the structure of the liverworts. 

The plants are of two kinds, male and female. The two dif- 
ferent organs, then, are developed on different plants. In 
appearance, however, before the beginning of the structures 
which bear the scxua! organs they are practically the same. The 
thallus is flattened like nearly all of the thalloid forms, and 
branches in a forked manner. The color is dark green, and 
through the middle line of the thallus the texture is different 
from that oi the margins, so that it possesses what we term a 



LIVERWORTS: MARCH A A 11 A. 



H5 



midrib, as shown in figs. 176, 180. The growing point of the 
thallus is situated in the little depression at the free end. If we 
examine the upper surface with a hand 
lens we see diamond-shaped areas, and 
at the center of each of these areas are 
the openings known as the stomates. 

317. Antheridial plants. — One of 
the male plants is figured at 176. It 
bears curious structures, 
each held aloft by a short 
stalk. These are the an- 
theridial recep- 
tacles (or male 
gametophores). 
Each one is cir- 
cular, thick, and f 
shaped some- Fig. 176. 

what like a bi- Male plant of marchantia bearing antheridiophores. 

convex lens. The upper surface is marked by radiating fur- 
rows, and the margin is crenate. Then we note, on careful 
examination of the upper surface, that there are numerous minute 
openings. If we make a thin section of this structure perpen- 









Fig. 177. 
Section of antheridial receptacle from male plant of Marchantia polymorpha, showing 
cavities where the antheridia are borne. 

dicular to its surface we shall be able to unravel the mystery of 
its interior. Here we see, as shown in fig. 177, that each one 
of these little openings on the surface is an entrance to quite 



146 



MORPHOLOG Y. 



a large cavity. Within each cavity there is an oval or ellip- 
tical body, supported from the base of the cavity on a short 
stalk. This is an antheridium, and one of them is shown still 
more enlarged in fig. 178. This shows the structure of the 
antheridium, and that there are within several angular areas, 
which are divided by numerous straight cross-lines into countless 
tiny cuboidal cells, the sperm mother cells. Each of these, as 
stated in the former chapter, changes into a swiftly moving body 
resembling a serpent with two long lashes attached to its tail. 

318. The way in which one of these sperm mother cells changes into this 
spermatozoid is very curious. We first note that a coiled spiral body is appear- 




Fig. 178. 
Section of antheridium of mar- 
chantia, showing the groups of 
sperm mother cells. 



Fig. 179. 
Spermatozoids of marchantia, 
uncoiling and one extended, show- 
ing the two cilia. 



ing within the thin wall of the cell, one end of the coil larger than the other. 
The other end terminates in a slender hair-like outgrowth with a delicate vesi- 
cle attached to its free end. This vesicle becomes more and more extended 
until it finally breaks and forms two long lashes which are clubbed at their 
free ends as shown in fig. 179. 

319. Archegonial plants. — In fig. 180 we see one of the 
female plants of marchantia. Upon this there are also very 
curious structures, which remind one of miniature umbrellas. 
The general plan of the archegonial receptacle (or female 



LIVER // r 0R TS : M. 1 R( 'If AN /'/./. 



147 



gametophore), for this is what these structures are, is similar to 
that of the antheridial receptacle, but the rays are more pro- 
nounced, and the details of structure are quite different, as we 
shall see. Underneath the arms there hang down delicate 
fringed curtains. If we make sections of this in the same direc- 




Fig. 180. 
Marchantia polymorpha, female plants bearing archegoniophores. 

tion as we did of the antheridial receptacle, we will be able to 
find what is secreted behind these curtains. Such a section is 
figured at 184. Here we find the archegonia, but instead of 
.being sunk in cavities their bases are attached to the under 



I48 MORPHOLOGY. 

surface, while the delicate, pendulous fringes afford them pro- 
tection from drying. An archegonium we see is not essentially 
different in marchantia from what it is in riccia, and it will be 
interesting to learn whether the sporogonium is essentially dif- 
ferent from what we find in riccia. 



CHAPTER XXIII. 

LIVERWORTS CONTINUED. 

320. Sporogonium of marchantia. — If we examine the plant 
shown in fig. 181 we will see oval bodies which stand out be- 




we can see 



Fig. 181. 

Archegonial receptacles of marchantia bearing ripe sporogonia The 
capsule of the sporogonium projects outside, while the stalk is attached to 
the receptacle underneath the curtain. In the left figure two of the 
capsules have burst and the elaters and spores are escaping. 

tween the rays of the female receptacle, supported 
on short stalks. These are the sporogonia, or 
spore-cases. We judge at once that they are quite 
different from those which we have studied in 
riccia, since those were not stalked. We can see 
that some of the spore-cases have opened, the wall 
splitting down from the apex in several lines. This 
is caused by the drying of the wall. These tooth- 
like divisions of the wall now curl backward, and 
the yellowish mass of the spores in slow motion, 

149 



ISO 



MORPHOLOGY. 



foiling here and there. It appears also as if there were twisting 
threads which aided the spores in becoming freed from the 
capsule. 




Fig. 182. 

Section of archegonial receptacle of Marchantiapolymorpha; ripe 
sporogonia. One is open, scattering spores and elaters ; two are 
still enclosed in the wall of the archegonium. The junction of the 
stalk of the sporogonium with the receptacle is the point of attach- 
ment of the sporophyte of marchantia with the gametophyte. 

321. Spores and elaters. — If we take a bit 
of this mass of spores and mount it in water 
for examination with the microscope, we will 
see that, besides the spores, there are very 
peculiar thread-like bodies, 
the markings of which remind 
one of a twisted rope. These 
are very long cells from (lie 
inner part of the spore-case, 
and their walls 
are marked by spi- 
ral thickenings. 
This causes them 
in dry ing,and also 
when they absorb 

Fig. 183. 
moisture, to twist Elater and spore of marchantia. sp, spore; mc, mother-cell of 
1 1 • 11 spores, showing partly formed spores. 

and curl in all 

sorts of ways. They thus aid in pushing the spores out of the 

capsule as it is drying. 

322. Sporophyte of marchantia compared with riccia.— 

We must recollect that the sporogonium in marchantia is larger 
than in riccia, and that it is also not lying in the tissue of the 
thallus, but is only attached to it at one side by a slender stalk. 



LI J 'EX WOR TS : MA R CM A XTIA . 



151 



This shows us an increase in the size and complex structure of 
this new phase of the plant, the sporophyte. This is one of the 
very interesting things which we have to note as we go on in the 
study of the higher plants. 





Fig. 184. 
Marchantia polymorpha, archegonium at the left with egg; archegonium at the right with 
young sporogonium ; /. curtain which hangs down around the archegonia ; e, egg; v, venter 
of archegonium ; n, neck of archegonium ; s/, young spoiogonium. 

323. Sporophyte dependent on the gametophyte for its nutri- 
ment. — We thus see that at no time during the development of the 
sporogonium is it independent from the gametophyte. This new 
phase of plants then, the sporophyte, has not yet become an in- 
dependent plant, but must rely on the earlier phase for sustenance. 

324. Development of the sporogonium. — It will be interesting to note 
briefly how the development of the marchantia sporogonium differs from that 
of riccia. The first division of the fertilized e^£ is the same as in riccia, that 
i> a wall which runs crosswise of the axis of the archegonium divides it 
into two cells. In marchantia the cell at the base develops the stalk, so 
that here there is a radical difference. The outer eel 1 forms the capsule. 
But here after the wall is formed the inner tissue does not all go to make 
spores, as is the case with riccia. But some of it forms the elaters. While 
in riccia only the outside layer of cells of the sporogonium remained sterile, 
in marchantia the basal half of the egg remains completely sterile and 



152 



MORPHOLOGY. 



develops the stalk, ana in the outer half the part which is formed from some 
of the inner tissue is also sterile. 




Fig. 185. 

Section of developing sporogonia of marchantia ; nt, nutritive tissue of gametophyte ; st, 
sterile tissue of sporophyte ; s/>, fertile part of sporophyte ; va, enlarged venter of arche- 
gonium. 

325. Embryo. — In the development of the embryo we can see all the way 

through this division line between the basal half, which is completely sterile. 

and the outer hall, which is the fertile part. In fig. 185 we see a young 

embryo, and it is nearly circular in section although it is composed of 

numerous cells. The basal half is attached to the base of the inner surface 

of the archegonium, and at this time the archegonium still surrounds it. The 

archegonium continues to grow then as the embryo grows, and we can see 

tin- remains of the shrivelled neck. The portion of the embryo attached to 

the base oi the archegonium i> the sterile pari and is called the *• toot," and 

later develops the stalk. The sporogonium during all tin- stages of its 

development derives it> nourishment from the gametophyte at this point <>t 



LIVERWORTS : MARCHANTIA. 



'53 



attachment at the base of the archegonium. Soon, as shown in fig. 185 at 
the right, the outer portion of the sporogonium begins to differentiate into 
the cells which form the elaters and those which form spores. These lie in 
radiating lines side by side, and form what is termed the archesporium. Each 

fertile cell forms lour spores just as in riccia. They are thus called tin 
mother cells of the spores, or spore mother cells. 

326. How marchantia multiplies. New plants of marchantia are formed 
by the germination of the spores, and growth of the same to the thallus. 

The plants may also be multiplied by parts of the old ones breaking away 
by the action of strong currents of water, and when they lodge in suitable 
places grow into well-formed plants. As the thallus lives from year to year 
and continues to grow and branch the older portions die off, and thus sepa- 
rate plants may be formed from a former single one. 

327. Buds, or gemmae, of marchantia. — But there is another way in which 
marchantia multiplies itself. If we examine the upper surface of such a 




Fig. 186. 
Marchantia plant with cupules and gemmae ; rhizoids below. 

plant as that shown in fig. 186, we will see that there are minute cup- 
shaped or saucer-shaped vessels, and within them minute green bodies. 
If we examine a few of these minute bodies with the microscope we will see 
that they are flattened, biconvex, and at two opposite points on the margin 
there i> an indentation similar to that which appears at the growing end of 
the old marchantia thallus. These are the growing points of these little 
bud-. When the\- free themselves from the cups they come to lie on one 



154 



MORPHOLOG V. 



side. It does not matter on what side they lie, for whichever side it is, that 
will develop into the lower side of the thallus, and forms rhizoids, while the 
upper surface will develop the stomates. 



Leafy-stemmed liverworts. 

328. We should now examine more carefully than we have 
done formerly a few of the leafy-stemmed liverworts (called 
foliose liverworts). 

329. Frullania (Fig. 6o). — This plant grows on the bark of 
logs, as well as on the bark of standing trees. It lives in quite 

dry situations. 
If we examine 
the leaves we 
will see how it is 
able to do this. 
We note that 
there are two 
rows of lateral 
leaves, which 
are very close 
together, so 
close in fact that 
they overlap 
like the shingles 
on a roof. 
Fig. 187. Then, as the 

Section of thallus of marchantia. A, through the middle portion ; 
B, through the marginal portion ; /, colorless layer; chl, chlorophyll Creeping Stems 
layer; ^/, stomate ; h, rhizoids; />, leaf-like outgrowths on under 

side (Goebei). lie very close to 

the bark of the tree, these overlapping leaves, which also 
hug close to the stem and bark, serve to retain moisture 
which trickles down the bark during rains. If we examine 
these leaves from the under side as shown in fig. 62, we see 
that the lower or basal part of each one is produced into a 
peculiar lobe which is more or less cup-shaped. This catches 
water and holds it during dry weather, and it also holds moisture 
which the plant absorbs during the night and in damp days. 




FOLIOSE LIVERWORTS, 



155 



There is so much moisture in these little pockets of the under 
side of the leaf that minute animals have found them good places 
to live in, and one frequently discovers them in this retreat. 
There is here also a third row of poorly developed leaves on the 
under side of the stem. 

330. Porella. — Growing in similar situations is the plant known as 
porella. Sometimes there are a lew plant- SH^ 

in a group, and at other times lar^e mat- ^f\ {: ¥^^ 
occur on the bark of a trunk. This plant. ^^^.W\ 
porella. also has closely overlapping leave- 
in rows on opposite sides of the stem, am 
the lower margin of each leaf is curved 
under somewhat as 



in frullania, though 

the pocket is not so 
well formed. 

The larger plants 
are female, that is 
the\' bear arfchego- 
nia, while the male 
plants, those which 
bear antheridia, are 
smaller and the an- 
theridia are borne 
on small lateral 
branches. The an- 
theridia are borne 
in the axils of the 
leaves. Others of 
the leafy- stemmed 
liverworts live in 
damp situations. 
Some of these, as 
Cephalozia. grow on damp rotten logs. Cephalozia is much more delicate. 
and the leaves are farther apart. It could not live in Mich dry situations 
where the frullania is sometimes found. If possible the two plants should be 
compared in order to see the adaptation in the structure and form to their 
environment. 

331. Sporogonium of a fcliose liverwort. — The sporogonium 
of the leafy-stemmed liverworts is well represented by that of 
several genera. We may take for this study the one illustrated 




Fig. 18 

Thallus of a thalloid liverwort (blasia) showing lobed 
margin of the frond, intermediate between thalloid and 
foliose plant. 



1 5 6 



MORPHOLOGY. 



in fig. 192, but another will serve the purpose just as well. V/e 
note here that it consists of a rounded capsule borne aloft on a 
long stalk, the stalk being much longer proportionately than in 
marchantia. At maturity the capsule splits down into four 




Fig. 189. 
Foliose liverwort, male plant showing anthe- 
ridia in axils of the leaves (a jungermannia). 




Fig. 190. 
Antheridium of a foliose liverwort (jun- 
germannia). 




Fig. 191. 
Foliose liverwort, female plant with 
rhizoids. 



quadrants, the wall forming four valves, which spread apart from 
the unequal drying of the cells, so that the spores are set free, as 
shown in fig. 194. Some of the cells inside of the capsule de- 
velop elaters here also as well as spores. These are illustrated 
in fig. 196. 

332, In this plant we see that the sporophyte remains attached 



FOLIOSE LIVERWORTS. 



'5; 



to the gametophyte, and thus is dependent on it for sustenance. 

This is true of all the plants of this 
group. The sporophyte never becomes 
capable of an independent existence, 
and yet we see that it is becoming 
larger and more highly differentiated 
than in the simple riccia. 




Fig. 193. 

Opening capsule 
showing escape of 
spores and elaters. 




Fig. 194. 

Capsule parted down 
to the stalk. 





Fig. 192. 

Fruiting plant of a foliose liver- pj g jg. 
wort (jungermannia). Leafy part 

is the gametophyte ; stalk and cap- Four spores from Elaters, at left showing the two 

sule is the sporophyte (sporogonium mother cell held in spiral marks, at right a branched 

in the bryophytes). a group. elater. 

Figs. 193-196. — Sporogonium of liverwort (jungermannia) opening by splitting into four 
parts, showing details of elaters and spores. 



CHAPTER XXIV. 

MOSSES (MUSCI). 

333. We are now ready to take up the more careful study of 
the moss plant. There are a great many kinds of mosses, and 
they differ greatly from each other in the finer details of struc- 
ture. Yet there are certain general resemblances which make it 
convenient to take for study almost any one of the common 
species in a neighborhood, which forms abundant fruit. Some, 
however, are more suited to a first study than others. (Polytri- 
chium and funaria are good mosses to study.) 

334. Mnium. — We will select here the plant shown in fig. 197. 
This is known as a mnium (M. afrme), and one or another of the 
species of mnium can be obtained without much difficulty. 
The mosses, as we have already learned, possess an axis 
(stem) and leaf-like expansions, so that they are leafy-stemmed 
plants also. Certain of the branches of the mnium stand upright, 
or nearly so, and the leaves are all of the same size at any given 
point on the stem, as seen in the figure. There are three rows 
of these leaves, and this is true of most of the mosses. 

335. The mnium plants usually form quite extensive and pretty 
mats of green in shady moist woods or ravines. Here and there 
among the erect stems are prostrate ones, with two rows of promi- 
nent leaves so arranged that it reminds one of some of the leafy- 
stemmed liverworts. If we examine some of the leaves of the 
mnium we will see that the greater part of the leaf consists of a 
single layer of green cells, just as is the case in the leafy-stemmed 
liverworts. But along the middle line is a thicker layer, so that 
it forms a distinct midrib. 'This is characteristic of the leaves 

158 



MOSSES, 



I 59 



of mosses, and is one way in which they are separated from the 
leafy-stemmed liverworts, the latter never having a midrib. 

336. The fruiting moss plant. — Infig. 197 is a moss plant "in 
fruit," as we say. Above the leafy stem a slender stalk beais 



<^ 





the capsule, and in this capsule are borne 
the spores. The capsule then belongs to 
the sporophyte phase of the moss plant, and 
we should inquire whether the entire plant 
as we see it here is the sporophyte, or 
whether part of it is gametophyte. If 
a part of it is gametophyte and a part 
sporophyte, then where does the one end 
and the other begin ? If we strip off the 
leaves at the end of the leafy stem, and 
make a longisection in the middle line, we 
should find that the stalk which bears the 
capsule is simply stuck into the end of the 




Fig. 197. 

Portion of moss plant of Mnium affine, showing two 
sporogonia from one branch. Capsule at left has just shed 
the cap or operculum ; capsule at right is shedding spores, 
and the teeth are bristling at the mouth. Next to the right 
is a young capsule with calyptra still attached ; next are 
two spores enlarged. 



leafy stem, and is not organically connected with it. This is 
the dividing line, then, between the gametophyte and the sporo- 
phyte. We shall find that here the archegonium containing 



i6o 



MORPHOLOGY. 



the egg is borne, which is a surer way of determining the limits 
of the two phases of the plant. 

337. The male and female moss plants. — The two plants of mnium shown in 
figs. 198, 199 are quite different, as one can easily see, and yet they belong 
to the same species. One is a female plant, while the other is a male plant. 

The sexual organs then in mnium, as 
in many others of the mosses, are borne 
on separate plants. The archegonia 
are borne at the end of the stem, and are 
protected by somewhat narrower leaves 
which closely overlap and are wrapped 
together. They are similar to the 
1 ) archegonia of the liverworts. 





Fig. 198. 
Female plant (gametophyte) of a moss 
(mnium), showing rhizoids below, and the 
tint of leaves above which protect the arche- 
gonia. 



Fig. 199. 
Male plant (gametophyte) of a moss 
(mnium) showing rhizoids below and the 
antheridia at the center above surrounded by 
the rosette of leaves. 



The male plants of mnium are easily selected, since the leaves at the end 
of the stem form a broad rosette with the antheridia, and some sterile threads 
packed closely together in the center. The ends of the mass of antheridia 
can be seen with the naked eye, as shown in tig. I99. When the antheridia 



A/OSs£S. 



161 



are ripe, if we make a section through a cluster, or if we merely tease out 
some from the end with a needle in a drop of water on the slide, then prepare 
for examination with the microscope, we will see the form of the antheridia. 
They are somewhat clavate or elliptical in outline, as seen in fig. 201. Be- 
tween them there stand short threads composed of several cells containing 
chlorophyll grains. These are sterile threads (paraphyses). 

338. Sporogonium. — In fig. 197 we see illustrated a sporogonium of mnium, 
which is of course developed Iron the fertilized agg cell of the archegonium. 
There is a nearly cylindrical capsule, bent downward, and supported on a long 




Fig. 201. 

r lg. 200. Antheridium of mnium 

Section through end of stem of female plant of mnium, show- with jointed paraphysis 
ing archegonia at the center. One archegonium shows the egg. at the left ; spermato- 
On the sides are sections of the protecting leaves. zoids at the right. 

slender stalk. Upon the capsule is a peculiar cap,* shaped like a ladle or 
spatula. This is the remnant of the old archegonium, which, for a time sur- 
rounded and protected the young embryo of the sporogonium, just as takes 
place in the liverworts. In most of the mosses this old remnant of the arche- 
gonium is borne aloft on the capsule as a cap, while in the liverworts it is 
thrown to one side as the sporogonium elongates. 
339. Structure of the moss capsule. — At the free end on the moss capsule 

* Called the calyptra. 



1 62 



MORPHOLOGY. 



as shown in the case of mnium in Fig. 197, after the remnant of the arche- 

gonium falls away, there is seen a conical lid which fits closely over the end. 

When the capsule is ripe this lid easily falls away, and can be brushed off 

so that it is necessary to handle the plants with care if it is 

desired to preserve this for study. 

340. When the lid is brushed away as the capsule dries 
more we see that the end of the capsule covered by the lid 
appears "frazzled." If we examine this end with the micro- 
scope we will see that the tissue of the capsule here is torn 
with great regularity, so that there are two rows of narrow, 
sharp teeth which project outward in a ring around the 
opening. If we blow our "breath" upon these teeth they 
will be seen to move, and as the 
moisture disappears and reappears 
in the teeth, they close and open 
the mouth of the capsule, so sensi- 
tive are they to the changes in the 
humidity of the air. In this way 
all of the spores are prevented to 
some extent from escaping from 
the capsule at one time. 

341. Note. If we make a sec- 
tion longitudinal of the capsule of 
mnium, or some other moss, we find 
that the tissue which develops the 
spores is much more restricted 
than in the capsule of the liver- 
worts which we have studied. The 
spore-bearing tissue is confined to 
a single layer which extends around 
the capsule some distance from the 
outside of the wall, so that a central 
left of sterile tissue. 





Fig. 202. 



Two different stages of young sporogonium of cylinder is 
a moss, still within the archegonium and wedg- This is the columella, and is pres- 
mg their way into the tissue of the end of the stem. r 

/i, neck of archegonium ; /, young sporogonium. ent in nearly all the mosses. Each 
This shows well the connection of the sporophyte r lt „ r ., r ,., ■. 

with the gametophyte. of the cells of the fertile layer 

divides into four spores. 
342. Development of the sporogonium. — The egg cell after fertilization 
divides by a wall crosswise to the axis of the archegonium. Each of these 
cells continues to divide for a time, so that a cylinder pointed at both ends is 
formed. The lower end of this cylinder of tissue wedges its way down 
through the base of the archegonium into the tissue of the end of the moss 
stem as shown in fig. 202. This forms the foot through which the nutrient 









MOSSES. 163 

materials are passed from the gametophyte to the sporogonium. The upper 
part continues to grow, and finally the upper end differentiates into the mature 

capsule. 

343. Protonema of the moss. — When the spores of a moss germinate they 
form a thread-like body, with chlorophyll. This thread becomes branched, 
and sometimes quite extended tangles of these threads are formed. This r 
called the protonema, that is first thread. The older threads become finally 
brown, while the later ones are green. From this protonema at certain 
points buds appear which divide by close oblique walls. From these buds 
the leafy stem of the moss plant grows. Threads similar to these protonemal 
threads now grow out from the leafy stem, to form the rhizoids. These 
supply the moss plant with nutriment, and now the protonema usually dies, 
though in some few species it persists for long periods. 



164 



MORPHOLOG y. 



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with spermato- 1 with egg in 
zoids. each. 


ial receptacles on 

Archegonia , 
borne on female 
gametophore (or 
archegonio- 
phore), each with 
an egg. 


On different plants. 

Antheridia, Archegonia, 
with spermato- each with egg, 
zoids, in axils of on female plant, 
leaves of male 
plant. 


Hit plants. 

Archegonia, 
each with egg, on 
female plant 
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on sporogonium 
is remnant of 
archegonium.) 


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different plants. 

An t he r idia, 
with spermato- 
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phores, or male 
gametophores 


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with spermato- 
zoids, at end 
of stem of male 
plant. 


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Multiplica- 
tion. 


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branching and 
dying away of 
older parts. 


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of older parts, 
and by gemmae. 


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by growth of pro- 
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Thallus flattened, 
ribbon-like, forked, 
or nearly circular. 


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ribbon-like, forked, 
male and female 
plants bear gameto- 
phores. 


A plant with ap- 
parent leaves and 
stem ; margins of 
thallus have become 
cut into lobes. Male 
and female plants. 


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of leaves (similar to 
jungermannia), borne 
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chia, 
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CHAPTER XXV. 

FERNS. 

345. In taking up the study of the ferns we find plants which 
are very beautiful objects of nature and thus have always attracted 
the interest of those who love the beauties of nature. But they 
are also very interesting to the student, because of certain re- 
markable peculiarities of the structure of the fruit bodies, and 
especially because of the intermediate position which they occupy 
within the plant kingdom, representing in the two phases of 
their development the primitive type of plant life on the one 
hand, and on the other the modern type. We will begin our 
study of the ferns by taking that form which is the more promi- 
nent, the fern plant itself. 

346. The Christmas fern. — One of the ferns which is very 
common in the Northern States, and occurs in rocky banks and 
woods, is the well-known Christmas fern (Aspidiumacrostichoides) 
shown in fig. 203. The leaves are the most prominent part of the 
plant, as is the case with most if not all our native ferns. The 
stem is very short and for the most part under the surface of the 
ground, while the leaves arise very close together, and thus form 
a rosette as they rise and gracefully bend outward. The leaf is 
elongate and reminds one somewhat of a plume with the pinnae 
extending in two rows on opposite sides of the midrib. These 
pinnae alternate with one another, and at the base of each pinna 
is a little spur which projects upward from the upper edge. 
Such a leaf is said to be pinnate. While all the leaves have the 
same general outline, we notice that certain ones, especially those 
toward the center of the rosette, are much narrower from the 

165 



1 66 



MORPHOLOGY. 



middle portion toward the end. This is because of the shorter 
pinnae here. 

347. Fruit "dots" (sorus, indusium). — If we examine the 
under side of such short pinnae of the Christmas fern we see that 
there are two rows of small circular dots, one row on either side of 
, the pinna. These are called the " fruit 
ts," or sori (a single one is a sorus). If 
examine it with a low power of the mi- 
croscope, 
or with a 
pocket 
lens, we 
willseethat 
there is a 
circular 
disk which 
c o vers 
more or 
less com- 
pletely very 
inute objects, nsual- 
the ends of the 
•rojecting just be- 
le edge if they are 
This circular disk 
is called the indu- 
nd it is a special 
th of the epidermis 
leaf here for the 
3U of the spore - 
These minute ob- 
jects underneath are the 
fruit bodies, which in the 
case of the ferns and their allies are called sporangia. This 
indusium in the case of the Christmas fern, and also in some 
others, is attached to the leaf by means of a short slender stalk 




Fig. 203. 
Christmas fern (Adiantum acrostichoides). 



FEFNS. 



167 



which is fastened to the middle of the under side of this shield, 

as seen in cross section in fig. 209. 

348. Sporangia. — If we section through the leaf at one of the 

fruit dots, or if we tease off some of the sporangia so that the 

stalks are still attached, and 
examine them with the mi- 
croscope, we can see the 
form and structure of these 
peculiar bodies. Different 
views of a sporangium are 
shown in fig. 210. The 
slender portion is the stalk, 
and the larger part is the 
spore-case proper. We 
should examine the structure 
of this spore-case quite care- 
fully, since it will help us to 
understand better than we 
otherwise could the remark- 
able operations which it 
performs in scattering the 
spores. 

349. Structure of a spo- 
rangium. — If we examine 
one of the sporangia in side 
view as shown in fig. 210, 
Fig. 204. we note a prominent row of 

Rhizome with bases of leaves, and roots of the ce H s which extend around 
Christmas fern. 

the margin of the dorsal 
edge from near the attachment of the stalk to the upper front 
angle. The cells are prominent because of the thick inner 
walls, and the thick radial walls which are perpendicular to the 
inner walls. The walls on the back of this row and on its 
sides are very thin and membranous. We should make this 
out carefully, for the structure of these cells is especially adapt- 
ed to a special function which they perform. This row of cells 




i68 



MORPHOLOGY. 



is termed the annulus, which means a little ring. While this 
is not a complete ring, in some other ferns the ring is nearly 
complete. 

350. In the front of the sporangium is another peculiar group 




Fig. 205. 
Rhizome of sensitive fern (Onoclea sensibilis). 

of cells. Two of the longer ones resemble the lips of some crea- 
ture, and since the sporangium opens between them they are 
sometimes termed the lip cells. These lip cells are connected with 

the upper end of the annulus on one 
side and with the upper end of the stalk 
on the other side by thin-walled cells, 
which may be termed connective cells, 
since they hold each lip cell to its part 
of the opening sporangium. The cells 
on the side of the sporangium are also 
thin -walled. If we now examine a 
sporangium from the back, or dorsal 

Fig. 206. 1 to 

Under side of pinna of Aspidium edge as we say, it will appear as in the 

spinulosum showing fruit dots . r . - r TT 

(soil). left-hand figure. Here we can see 

how very prominent the annulus is. It projects beyond the 
surface of the other cells of the sporangium. The spores are 
contained inside this case. 




FERNS. 



169 



351. Opening of the sporangium and dispersion of the 
spores. — If we take some fresh fruiting leaves of the Cpristmas 

fern, or of any one of many of the species of the true ferns just 
at the ripening of the spores, and place a portion of it on apiece 
of white paper in a dry room, in a very short time we will sde 
that the paper is being dusted with minute brown objects which 
fly out from the leaf. Now if we take a portion of the same leaf 
and place it under the low power of the microscope, so that the 
full rounded sporangia can be seen, in a short time we will note 
that the sporangium opens, the upper half curls backward as 




Fig. 207. 
Four pinnae of adiantum, showing recurved margins which cover the sporangia. 

shown in fig. 211, and soon it snaps quickly, to near its former 
position, and the spores are at the same time thrown for a consid- 
erable distance. This movement can sometimes be seen with the 
aid of a good hand lens. 

352. How does this opening and snapping of the sporan- 
gium take place ? — We are now more curious than ever to see 
just how this opening and snapping of the sporangium takes place. 
We should now mount some of the fresh sporangia in water and 
cover with a cover glass for microscopic examination. A drop 
of glycerine should be placed at one side of the cover glass on the 
slip so that the t:d'^c of the glycerine will come in touch with the 
water. Now as one looks through the microscope to watch the 



170 



MORPHOLOGY. 



sporangia, the water should be drawn from under the cover glass 
with the aid of some bibulous paper, like filter paper, placed at the 

edge of the cover glass on 
the opposite side from the 
glycerine. As the glycer- 
ine takes the place of the 
water around the sporangia 
it draws the water out of 
the cells of the annulus, 
just as it took the water 
out of the cells of the 
spirogyra as we learned 
some time ago. As the 
water is drawn out of these 
cells there is produced a 
pressure from without, the 
atmospheric pressure upon 
the glycerine. This causes 
the walls of these cells of 
the annulus to bend in- 
ward, because, as we have 
already learned, the glycer- 

Section through sorus of Polypodium vulgare J ne does not pass through 

showing dilterent stages ot sporangium, and one ' ° 

multicellular capitate hair. tne wa l] s nearly SO fast 

as the water comes out. 

353. Now the structure of the cells of this annulus, as we 
have seen, is such that the inner walls and the perpendicular 





Fig 
Section through sorus and shield-shaped indusium ofaspicBum. 

walls arc stout, and consequently they do not bend or collapse 
when this pressure is brought to bear on the outside of the cells. 



FF.AW'S. 



IJI 



The thin membranous walls on the back (dorsal walls) and on 
the sides of the annulus, however, yield readily to the pressure 
and bend inward. This, as we can readily see, pulls on the ends 
of each of the perpendicular walls drawing them closer together. 
This shortens the outer surface of the annulus and causes it to 
first assume a nearly straight position, then curve backward until 
it quite or nearly becomes doubled on itself. The sporangium 




Fig. 210. 
Rear, side, and front views of fern sporangium. 



, annulus; <i, lip cells. 



opens between the lip cells on the front and the lateral walls of 
the sporangium are torn directly across. The greater mass of 
spores are thus held in the upper end of the open sporangium, 
and when the annulus has nearly doubled on itself it suddenly 
snaps back again in position. While treating with the glycerine 
we can see all this movement take place. Each cell of the 
annulus acts independently, but often they all act in concert. 
When they do not all act in concert, some of them snap sooner 
than others, and this causes the annulus to snap in segments. 

354. The movements of the sporangium can take place in 
old and dried material. — If we have no fresh material to study 



172 



MORPHOLOGY. 



the sporangium with, we can use dried material, for the move- 
ments of the sporangia can be well seen in dried material, pro- 
vided it was collected at about the time the sporangia are mature, 
that is at maturity, or soon afterward. We take some of the 
dry sporangia (or we may wash the glycerine off those which we 
have just studied) and mount them in water, and quickly examine 




O^ 






^P^^~ 






GT 




* \ x \ \\ 



Fig. 211. 

Dispersion of spores from sporangium of Aspidium acrostichoides, showing different 
stages in the opening and snapping ol the annulus. 

them with a microscope. We notice that in each cell of the 
annulus there is a small sphere of some gas. The water which 
bathes the walls of the annulus is absorbed by some 4 substance 
inside these cells. This we can see because of the fact that this 
sphere of gas becomes smaller and smaller until it is only a mere 



1 



FEJRNS. 173 

dot, when it disappears in a twinkling. The water has been taken 
in under such pressure that it has absorbed all the gas, and the 
farther pressure in most cases closes the partly opened sporangium 
more completely. 

355. Now we should add glycerine again and draw out the 
water, watching the sporangia at the same time. We see that 
the sporangia which have opened and snapped once will do it 
again. And so they may be made to go through this operation 
several times in succession. We should now note carefully the 
annulus, that is after the sporangia have opened by the use of 
glycerine. So soon as they have snapped in the glycerine we can 
see those minute spheres of gas again, and since there was no air 
on the outside of the sporangia, but only glycerine, this gas must, 
it is reasoned, have been given up by the water before it was all 
drawn out of the cells. 

356. The common polypody. — We may now take up a few other ferns for 
study. Another common fern is the polypody, one or more species of which 
have a very wide distribution. The stem of this fern is also not usually seen, 
but is covered with the leaves, except in the case of those species which grow 
on the surface of rocks. The stem is slender and prostrate, and is covered 
with numerous brown scales. The leaves are pinnate in this fern also, but we 
find no difference between the fertile and sterile leaves (except in some rare 
cases). The fruit-dots occupy much the same positions on the under side of the 
leaf that they do in the Christmas fern, but we cannot find any indusium. In 
the place of an indusium are club-shaped hairs as shown in fig. 208. The en- 
larged ends of these clubs reaching beyond the sporangia give some protection 
to them when they are young. 

357. Other ferns. — We might examine a series of ferns to see how different 
they are in respect to the position which the fruit dots occupy on the leaf. The 
common brake, which sometimes covers extensive areas and becomes a trouble- 
some weed, has a stout and smooth underground stem (rhizome) which is often 
12 to 20 cm beneath the surface of the soil. There is a long leaf stalk, which 
bears the lamina, the latter being several times pinnate. The margins of the 
fertile pinna? are inrolled, and the sporangia are found protected underneath 
in this long sori along the margin of the pinna. The beautiful maidenhair fern 
and its relatives have obovate pinnce, and the sori are situated in the same posi- 
tions as in the brake. In other ferns, as the walking fern, the sori are borne 
along by the side of the veins of the leaf. 

358. Opening of the leaves of ferns. — The leaves of ferns open in a peculiar 
manner. The tip of the leaf is the last portion developed, and the growing 



174 



MORPHOLOG Y. 



leaf appears as if it was rolled up as in fig. 204 of the Christmas fern. As the 
leaf elongates this portion unrolls. 

359. Longevity of ferns. — Most ferns live from year to year, by growth 
adding to the advance of the stem, while by decay of the older parts the stem 
shortens up behind. The leaves are short-lived, usually dying down each 
year, and a new set arising from the growing end of the stem. Often one can 
see just back or below the new leaves the old dead ones of the past season, 
and farther back the remains of the petioles of still older leaves. 

360. Budding of ferns. — A few 
ferns produce what are called bulbils 
or bulblets on the leaves. One of 
these, which is found throughout the 
greater part of the eastern United 
States, is the bladder fern (Cystop- 
teris bulbifera), which grows in shady 
rocky places. The long graceful 
delicate leaves form in the axils of 
the pinnae, especially near the end of 
the leaf, small oval bulbs as shown 
in fig. 212. If we examine one of 
these bladder-like bulbs we see that 
the bulk of it is made up of short 
thick fleshy leaves, smaller ones ap- 
pearing between the outer ones at the 
smaller end of the bulb. This bulb 
contains a stem, young root, and 
several pairs of these fleshy leaves. 
They easily fall to the ground or 
rocks, where, with the abundant 
moisture usually present in localities 

where the fern is found, the bulb 
Fig. 212. 

Cvstopteris bulbifera, young plant growing grows until the roots attach the plant 
from bulb. At right is young bulb in axil of tQ the soil or m tne cre vices of the 
pinna of leaf. 

rocks. A young plant growing from 

one of these bulbils is shown in fig. 212. 

361. Greenhouse ferns. — Some of the ferns grown in conservatories have 
similar bulblets. Fig. 213 represents one of these which is found abundantly 
on the leaves of Asplenium bulbiferum. These bulbils have leaves which are 
very similar to the ordinary leaf except that they are smaller. The 
bulbs are also much more firmly attached to the leaf, so that they do not 
readily fall away. 

362. Plant conservatories usually furnish a number of very interesting 
terns, and one should attempt to make the acquaintance of some of them, for 




■FiTiF.V.s. 



175 



here one has an opportunity during the winter season not only to observe these 

interesting plants, but also to obtain material for study. In the tree i'erns 
which often are seen growing in such places we see examples of the massive 
trunks and leaves of some of the tropical species. 

363. The fern plant is a sporophyte. — We have now studied 
the fern plant, as we eall it, and we have found it to represent 
the spore-bearing phase of the plant, that is the sporophyte (cor- 
responding to the sporogonium of the liverworts and mosses). 

364. Is there a ga- 
in etophyte phase in 
ferns ? — But in the spor- 
ophyte of the fern, which 
we should not forget is 
the fern plant, we have 
a striking advance upon 
the sporophyte of the 
liverworts and mosses. 
In the latter plants the 
sporophyte remained 
attached to the gameto- 
phyte, and derived its 
nourishment from it. 
In the ferns, as we see, 
the sporophyte has a 
root of its own, and is 
attached to the soil. 
Through the aid of root 

hairs of its own it takes up mineral solutions. It possesses also 
a true stem, and true leaves in which carbon conversion takes 
place. It is able to live independently, then. Does a gametophyte 
phase exist among the ferns? Or has it been lost ? If it does 
exist, what is it like, and where does it grow? From what we 
have already learned we should expect to find the gametophyte 
begin with the germination of the spores which are developed 
on the sporophyte, that is on the fern plant itself. We should 
investigate this and see. 




Fig. 213. 
Bulbil growing from leaf of asplenium {A , bulbifenim). 



CHAPTER XXVI. 



FERNS CONTINUED. 

Gametophyte of ferns. 

365. Sexual stage of ferns. — We now wish to see what the 
sexual stage of the ferns is like. Judging from what we have 
found to take place in the liverworts and mosses we would infer 




Fig ?.i 4 . 
Prothallium of fern, under sick-, showing rhizoids, antheridia scattered among and near 
them, and the archegonia in ar the sinus. 

that the form of the plain which bears the sexual organs is de- 
veloped from the spores. Tins is true, and if we should examine 



)ld 



(lcca\ in Li' LOgS, o 



r decaying wood in damp places in the near 

i7<< 



FERNS. 



177 




Fig. 215. 
Spore of Pteris serru- 
lata showing the three- 
rayed elevation along 
the side of which the 
spore wall cracks during 
germination. 



vicinity of ferns, we would probably find tiny, green, thin, heart- 
shaped growths, lying (-lose to the substratum. These are also 
found quite frequently on the soil of pots in plant conservatories 

where ferns are grown. Gardeners also in conservatories usually 

sow fern spores to raise new fern plants, 

and usually one can find these heart-shaped 

growths on the surface of the soil where 

they have sown the spores. We may call 

the gardener to our aid in finding them in 

conservatories, or even in growing them for 

us if we cannot find them outside. In some 

cases they may be grown in an ordinary room 

by keeping the surfaces where they are 

growing moist, and the air also moist, by 

placing a glass bell jar over them. 

366. In fig. 214 is shown one of these growths enlarged. 
Upon the under side we see numerous thread-like outgrowths, 
the rhizoids, which attach the plant to the substratum, and which 
act as organs for the absorption of nourishment. The sexual 

organs are 



borne on the 
under side also, 
and we will 
study the m 
a t e r . This 
heart-shaped, 
flattened, thin, 
pore and green plant is 
the pruthdllium 

of ferns, and we should now give it more careful study, be- 
ginning with the germination of the spores. 

367. Spores. — We can easily obtain material for the study of 

the spores of ferns. The spores vary in shape to some extent. 

Many of them are shaped like a three-sided pyramid. One of 

is shown in fig. 215. The outer wall is roughened, and 

on one end are three elevated ridges which, radiate from a given 




Fig. 216. 
Spore of Adiantum 
acrostichoides with 
winged exospore. 



Fig. 217. 
Spore crushed to remove e: 
show endospore. 



1 7 8 



MORPHOLOGY. 




Fig. 218. 
Spores of asplenium ; exospore re 
moved from the one at the right. 



point. A spore of the Christmas fern is shown in fig. 216. The 
outer wall here is more or less winged. At fig. 217 is a spore 

of the same species from which the 
outer wall has been crushed, showing 
that there is an inner wall also. If 
possible we should study the germi- 
nation of the spores of some fern. 

368. Germination of the spores. 
— After the spores have been sown for 
about one week to ten days we should 
mount a few in water for examination 
with the microscope in order to study 
the early stages. If germination has begun, we will find that here 
and there are short slender green threads, in many cases attached 

to brownish bits, the old 
walls of the spores. 
Often one will sow the 
sporangia along with the 
spores, and in such cases 
there may be found a 
number of spores still 
within the old sporan- 
gium wall that are ger- 
minating, when they will 
appear as in fig. 219. 

369. Protonema. — 
These short green threads 
are called protonemal threads, ox protonema, 
which means a first thread, and it here 
signifies that this short thread only pre- 
cedes a larger growtli of the same object. 
In figs. 219, 220 are shown several stages of 
germination of different spores. Soon after 
Germinfting^TporcB of the short germ tube emerges from the 
!p ( Vran.<u 1 m m ' 1 ^ ' m the crack in the spore wall, it divides by the 





FEAXS. 



179 



formation of a cross wall, and as it increases in length other 
cross walls are formed. But very early in its growth we see that 
a slender outgrowth takes place from the cell nearest the old 
spore wall. This slender thread 
is colorless, and is not divided 
into cells. Jt is the first rhizoid, 
and serves both as an organ of 
attachment for the thread, and for 
taking up nutriment. 

370. Prothallium. — Aery soon, 
if the sowing has not been so 
crowded as to prevent the young 
plants from obtaining nutriment 
sufficient, we will see that the end 
of this protonema is broadening, 
as shown in fig. 220. This is done 
by the formation of the cell walls 
in different directions. It now 
continues to grow in this way, the 
end becoming broader and broader, 
and new rhizoids are formed from 
the under surface of the cells. The 
growing point remains at the mid- 
dle of the advancing margin, and 
the cells which are cut off from 
either side, as they become old, 
widen out. In this way the 
" wings," or margins of the bolus )- 
little, green, flattened body, are in advance of the growing 
point, and the object is more or less heart-shaped, as shown 
in fig. 214. Thus we see how the prothallium of ferns is 
formed. 

371. Sexual organs of ferns. — If we take one of the prothal- 
lia of ferns which have grown from the sowings of fern spores, 
or one of those which may be often found growing on the soil 




Fig. 220. 
Young prothallium of a fern (nipho- 



i8o 



MORPHOLOG V. 



of pots in conservatories, mount it in water on a slip, with 
the under side uppermost, we can then examine it for the 




Fig. 221. 
Male pro thallium of a fern (niphobolus), in form of an alga or protonema. Spermato- 
zoids escaping from antheridia. 

sexual organs, for these are borne in most cases on the under 
side. 

372. Antheridia. — If we search among the rhizoids we will 
see small rounded elevations as shown in fig. 214 or 222 scat- 




Fig. 222. 
Male prothallium of fern (niphobolus), showing opened and unopened antheridia ; 39, sec- 
tion oi unopened antheridium; y>. spermatozoids es< aping; 41 , spermatozoids which did not 
e < ape from the antheridium. 



FERNS. 



181 




tered over this portion of the prothallium. These are the an- 
theridia. Ifthepro- 
thallia have not been 
watered for a day or 
so, we may have an 
opportunity of see- 
ing the spermato- 
zoids coming out of 
the antheridium, for 
when the prothallia c .. , +1 ... . lg- . 223 ' 

1 Section of anthendia showing sperm cells, and spermato- 

are freshly placed in «>ids in the one at the right. 

water the cells of the antheridium ab- 
sorb water. This presses on the con- 
tents of the antheridium and bursts the 
cap cell if the antheridium is ripe, and 
all the spermatozoids are shot out. 
We can see here that each one is 
shaped like a screw, with the coils at 

Fig. 224. r ' 

Different views of spermatozoids; first close. But as the SpermatOZOid 
42, 43, in a quiet condition; 44, in , , . . r 

motion (Adiantum concinnum). begins tO move this COlI Opens SOme- 

what and by the vibration of 
the long cilia which are on the 
smaller end it whirls away. In 
such preparations one may often 
see them spinning around for a 
long while, and it is only when 
they gradually come to rest 
that one can make out their 
form. 

373. Archegonia. — If we now 
examine closely on the thicker 
part of the under surface of the 
prothallium, just back of the 
" sinus," we may see 





Fig. 225. 

Archegonium of fern. Large cell in the 
longer venter is the egg, next is the ventral canal 



.«») and in the canal of the neck are two 
StOUt projections from the Surface nuclei of the canal cell. 

of the prothallium. These are shown in fig. 214. They are 



182 



MORPHOLOGY. 



the archegonia. One of them in longisection is shown in fig. 
225. It is flask-shaped, and the broader portion is sunk in the 




Fig. 226. 
Mature and open archegonium of fern (Adiantum cuneatum) with spermatozoids making 
their way down through the slime to the egg. 

tissue of the pro thallium. The egg is in the larger part. The 
spermatozoids when they are swimming 
around over the under surface of the pro- 
thallium come near the neck, and here they 
are caught in the viscid substance which 
has oozed out of the canal of the arche- 
gonium. From here they slowly swim 
down the canal, and finally one sinks into 
the egg, fuses with the nucleus of the latter, 
and the egg is then fertilized. It is now 
ready to grow and develop into the fern 
plant. This brings us back to the sporo- 

phyte, which begins with the fertilized egg. 




Fig. 227. 

Fertilization in a fern 
< Marattia). s/>, spermato- 
zoid fusing with the nu- 
cleus of the egg. (After 
Campbell.) 



Sporophyte. 

374. Embryo. — The egg first divides into two cells as shown in fig. 228, then 
into four. Now from each one of these quandrants of the embryo a definite 
part oi the plant develops, from one the first leaf, from one the stem, from 
one the root, and from the other the organ which is called the foot, and which 



FERNS. 



18: 



attaches the embryo to the prothallium, and transports nourishment for the 
embryo until it can become attached to the soil and lead an independent ex- 
istence. During this time the wall of the archegonium grows somewhat to 

accommodate the increase in size of the embryo, as shown in tigs. 229, 230. 
But soon the wall of the archegonium is ruptured and the embryo emerges, 
the root attaches itself to the soil, and soon the prothallium dies. 

The embryo is first on the under side of the prothallium, and the first leaf 




Fig. 228. 
Two-celled embryo of Pteris serrulata. Remnant of archegonium neck below. 

and the stem curves upward between the lobes of the heart-shaped body, and 
then grows upright as shown in fig. 231. Usually only one embryo is formed 
on a single prothallium, but in one case I found a prothallium with two well- 
formed embryos which are figured in 232. 

375. Comparison of ferns with liverworts and mosse?. — In the ferns then 
we have reached a remarkable condition of things as compared with that 
which we found in the mosses and liverworts. In the mosses and liverworts 



1 84 



MORPHOLOG Y. 



the sexual phase of the plant (gametophyte) was the prominent one, 
and consisted of either a thallus or a leafy axis, but in either case it bore the 
sexual organs and led an independent existence; that is it was capable of ob- 
taining its nourishment from the soil or water by means of organs of absorp- 
tion belonging to itself, and it also performed the office of carbon conversion. 
376. The spore-bearing phase (sporophyte) of the liverworts and mosses, 
on the other hand, is quite small as compared with the sexual stage, and it is 




Fig. 22.;. 



ryo of fern (Adiantum concinnum) in enlarged venter of the archegonium. S 
leaf or cotyledon ; A\ root ; F, foot. 



Young embryo of fern (Adiantum 
stem ; /., first 



completely dependent on the sexual stage lor Its nourishment, remaining at- 
tached permanently throughout all it^ development, by means of the organ 
called a toot, , uid it die- after the spores are mature. 

377. Now in the ferns we see several striking differences. In the first 
pi, ice. as we have already observed, the spore-bearing phase (sporophyte) of 



FERNS. 



I8 5 



the plant is the prominent one. and thai which characterizes the plant. It 
also leads an independent existence, and. with the exception of a few eases, 
does not die after the development of the spores, but lives from year to year 
and develops successive crops of spores. There is a distinct advance here in 
the size, complexity, and permanency of this phase oi the plant. 

378. On the other hand the sexual phase of the ferns (gametophyte), while 
it still is capable of leading an independent existence, i> short-lived (with very 
lew exceptions). It is also much smaller than most of the liverworts and 




Embryo of fern i Adiantum concinnum) still surrounded by the archegonium, which has 
grown in size, forming the " calyptra." L, leaf; S, stem; A', root; J*\ foot. 



mosses, especially as compared with the size of the spore-bearing phase. 
The gametophyte phase or stage of the plants, then, is decreasing in size and 
durance as the sporophyte stage is increasing. We shall be interested to see 
if this holds good of the fern allies, that is of the plants which belong to the 
same group as the ferns. And as we come later to take up the stud}' of the 
higher plants we must bear in mind to cany on this comparison, and -re- if 
this progression on the one hand of the sporophyte continues, and if the 
retrogression of the gametophyte continues also. 



1 86 



MORPHOLOGY. 





Fig. 231. 
Young plant of Pteris sernilata still 
atta< lied to prothallium. 



Fig. 232. 
Two embryos from one prothallium of 
Vdiantum 1 uueatum, 



CHAPTER XXVII. 

HORSETAILS. 



379. Among the relatives of the ferns are the 
horsetails, so called because of the supposed resem- 
blance of the branched stems of some of the species 
to a horse's tail, as one might infer from the plant 
shown in fig. 23^ They do not bear the least re- 
semblance to the ferns which we have been study- 
ing. But then relationship in plants does not depend 
on mere resemblance of outward form, or of the promi- 
nent part of the plant. 

380. The field equisetum. Fertile shoots. — Fig. 
233 represents the common horsetail (Equisetum ar- 
vense). It grows in moist sandy or gravelly places, 
and the fruiting portion of the plant (for this species 
is dimorphic), that is the portion which bears the 
spores, appears above the ground early in the spring. 
It is one of the first things to peep out of the recently 
frozen ground. This fertile shoot of the plant does 
not form its growth this early in the spring. Its 
development takes place under the ground in the 
autumn, so that with the advent of spring it pushes 
up without delay. This shoot is from 10 to 20 
cm high, and at quite regular intervals there are 
slight enlargements, the nodes of the stem. The 
cylindrical portions between the nodes are the 
internodes. If we examine the region of the inter- 
nodes carefully we note that there are thin mem- E^iL^m^ 
branous scales, more or less triangular in outline, and whor e is ShOW1 ol 
connected at their bases into a ring around the stem. fStSg^spUre! 

187 



Fig. 233. 
Portion of 




188 MORPHOLOGY. 

Curious as it may seem, these are the leaves of the horsetail. 
The stem, if we examine it farther, will be seen to possess numer- 
ous ridges which extend lengthwise and which alternate with 
furrows. Farther, the ridges of one node alternate with those 
of the internode both above and below. Likewise the leaves 
of one node alternate with those of the nodes both above and 
below. 

381. Sporangia. — The end of this fertile shoot we see pos- 
sesses a cylindrical to conic enlargement. This is the fertile 

spike, and we note that its surface is marked off 
into regular areas if the spores have not yet been 
disseminated. If we dissect off a few of these por- 
tions of the fertile spike, and examine one of them 
with a low magnifying power, it will appear like the 
fig. 234. We see here that the angular area is a 
Fig. 234. disk-shaped body, with a stalk attached to its inner 
phyficr/equfsSum 8111 *^ 06 ? aR d with several long sacs projecting from 
ing e s ^Xngfa °on i ts inner face parallel with the stalk and surrounding 
the same. These elongated sacs are the sporangia, 
and the disk which bears them, together with the stalk which 
attaches it to the stem axis, is the sporophyil, and thus belongs to 
the leaf series. These sporophylls are borne in close whorls on 
the axis. 

382. Spores. — When the spores are ripe the tissue of the 
sporangium becomes dry, and it cracks open and the spores fall 
out. If we look at fig. 235 we will see that the spore is covered 
with a very singular coil which lies close to the wall. When the 
spore dries this uncoils and thus rolls the spore about. Merely 
breathing upon these spores is sufficient to make them perform 
very curious evolutions by the twisting of these four coils which 
are attached to one place of the wall. They are formed by the 
splitting up of an outer wall of the spore. 

383. Sterile shoot of the common horsetail. — When the 
spores are ripe they are soon scattered, and then the fertile 
shoot dies down. Soon afterward, or even while some of the 
fertile shoots are still in good condition, sterile shoots of the 



HORSETAILS. 



189 



plant begin to appear above the ground. One of these is shown 
in fig. 237. This has a much more slender stem and is pro- 





Fig. 235. 

Spore oi equisetum 

,\ith elaters coiled up. 



Fig. 236. 
Spore of equisetum with elaters un- 
coiled. 



vided with numerous branches. If we ex- 
amine the stem of this shoot, and of the 
branches, we will see that the same kind of 
leaves are present and that the markings on 
the stem are similar. Sinee the leaves of 
the horsetail are membranous and not green, 
the stem is green in color, and this per- 
forms the function of carbon conversion. 
These green shoots live for a great part of 
the season, building up material which is 
carried down into the underground stems, 
where it goes to supply the forming fertile 
shoots in the fall. On digging up some of 
these plants we see that the underground 
stems are often of great extent, and that 
both fertile and sterile shoots are attached 
to one and the same. 

384. The scouring rush, or shave grass. 
— Another common species of horsetail in 
the Northern States grows on wet banks, 
or in sandy soil which contains moisture 
along railroad embankments. It is 
the scouring rush (E. hyemale), so 
(ailed because it was once used for 
polishing purposes. This plant like 
all the species of the horsetails has 




Fig 237. 

Sterile plant of horsetail (Equi- 
setum arvensis; 



1 90 MORPHOLOG Y. 

underground stems. But unlike the common horsetail, there is 
but one kind of aerial shoot, which is green in color and fertile. 
The shoots range as high as one meter or more, and are quite 
stout. The new shoots which come up for the year are un- 
branched, and bear the fertile spike at the apex. When the 
spores are ripe the apex of the shoot dies, and the next season 
small branches may form from a number of the nodes. 

385. Gametophyte of equisetum. — The spores of equisetum have chloro- 
phyll when they are mature, and they are capable of germinating as soon as 
mature. The spores are all of the same kind as regards size, just as we 
found in the case of the ferns. But they develop prothallia of different 
sizes, according to the amount of nutriment which they obtain. Those 
which obtain but little nutriment are smaller and develop only antheridia, 
while those which obtain more nutriment become larger, more or less 
branched, and develop archegonia. This character of an independent pro- 
thallium (gametophyte) with the characteristic sexual organs, and the also 
independent sporophyte, with spores, shows the relationship of the horsetails 
with the ferns. We thus see that these characters of the reproductive 
organs, and the phases and fruiting of the plant, are more essential in deter- 
mining relationships of plants than the mere outward appearances. 



CHAPTER XXVIII. 

CLUB MOSSES. 

386. What are called the ' ' club mosses ' ' make up another 
group oi interesting plants which rank as allies of the ferns. 
They are not of course true mosses, but the general habit of 
some of the smaller species, and especially the 
form and size of the leaves, suggest a resem- 
blance to the larger of the moss plants. 

387. The clavate lyeopodium. — Here is one 
of the club mosses (fig. 238) which has a wide 
distribution and which is well entitled to hold 
the name of (dub because of the form of the up- 
right club-shaped branches. As will be seen 
from the illustration, it has a prostrate stem. 
This stem runs for considerable distances on 
the surface of the ground, often partly buried in 
the leaves, and sometimes even buried beneath 
the soil. The leaves are quite small, are flat- 
tened-awl-shaped, and stand thickly over the 
stem, arranged in a spiral manner, which is the 
usual arrangement of the leaves of the club 
mosses. Here and there are upright branches 
which are forked several times. The end of 
one or more of these branches becomes pro- 
duced into a slender upright stem which is T ' 

1 ° Lyeopodium c 1 u v a - 

nearlv leafless, the leaves being reduced to tum, branch bearing two 

o fruiting spikes; at right 

mere scales. The end of this leafless branch sporophyll with open 

sporangium : single 

then terminates in one or several cylindrical s P orenear it- 
heads which form the club. 




191 



192 



MORPHOLOGY. 



388 Fruiting spike of Lycopodium clavatum. — This club is 
the fruiting spike or head (sometimes termed a slrobiliis). Here 
the leaves are larger again and broader, but still not so large as 
the leaves on the creeping shoots, and they are paler. If we bend 
down some of the leaves, or tear off a few, we will see that in the 
axil of the leaf, where it joins the stem, there is a somewhat 
rounded, kidney -shaped body. This is the spore -case or spo- 
rangium, as we can see by an examination of its contents. There 
is but a single spore- case for each of the fertile leaves (sporophyll). 
When it is mature, it opens by a crosswise slit as seen in fig. 238. 
When we consider the number of spore -cases in one of these club- 
shaped fruit bodies Ave see that the number of spores developed 
in a large plant is immense. In mass the spores make a very fine, 
soft powder, which is used for some 
kinds of pyrotechnic material, and for 
various toilet purposes. 

389. Lycopodium lucidulum. — Another com- 
mon species is figured at 239. This is Lycopo- 
dium lucidulum. The habit of the plant is quite 
different. It grows in damp ravines, woods, and 
moors. The older parts of the stem are prostrate, 
while the branches are more or less ascending. 
It branches in a forked manner. The leaves are 
larger than in the former species, and they are 
all of the same size, there being no appreciable 
difference between the sterile and 
fertile ones. The characteristic 
club is not present here, but the 
spore-cases occupy certain regions of 
the stem, as shown at 239. In a 
single season one region of the stem 
may bear spore-cases, and then a 
sterile portion of the same stem is 
,. . . . f ' " .... ., c developed, which later bears another 

Lycopodium lucidulum, bulbils in axils <>t ■ 

leaves near the top, sporangia in axils of Leaves series of spore eases higher up. 
below them. At right is a bulbil enlarged. ^^ _ .... _, ,. 

390. Bulbils on Lycopodium 

lucidulum. — There LS one curious way in which this club moss multiplies. 
One may see frequently among the upper leaves small wedge-shaped or heart- 
shaped green bodies but little Larger than the ordinary haves. These are little 




LITTLE CLUB MOSSES. 



'93 



lmds which contain rudimentary shoot and root and several thick green leaves. 
When they fall to the ground the}' grow into new lycopodium plants, just as 
the bulbils of cystopteris do which were described in the chapter on ferns. 

391. Note. — The prothallia of the species of lycopodium which have been 
studied are singular objects. In L. cernuum a cylindrical body sunk in the 
earth is formed, and from the upper surface there are green lobes. In L. 
phlegmaria and some others slender branched, colorless bodies are formed 
which according to Treub grow as a saphrophyte in decayed bark of trees. 
Many of the prothallia examined have a fungus growing in their tissue which 
is supposed to play some part in the nutrition of the prothallium. 



The little club mosses (selaginella). 



392. Closely related to the club mosses are the selaginellas. 
These plants resemble closely the general habit of the club mosses, 
but are generally smaller and the leaves more delicate. Some 
species are grown in conservatories for ornament, the leaves of 





Fig. 240. Fig. 24;. Fig. 242. Fig. 243. 

Selaginella w i t h Fruiting spike Large spo- Small spo- 

three fruiting spikes, showing large and rangium. rangium. 

(Selaginella apus.) small sporangia. 

such usually having a beautiful metallic lustre. The leaves of some 
are arranged as in lycopodium, but many species have the leaves 
in four to six rows. Fig. 240 represents a part of a selaginella 
plant (S. apus). The fruiting spike possesses similar leaves, but 
they are shorter, and their arrangement gives to the spike a four- 
sided appearance, 



194 



MORPHOLOG Y. 



393. Sporangia. — On examining the fruiting spike, we find 
as in lycopodium that there is but a single sporangium in the 
axil of a fertile leaf. But we see that they are of two different 
kinds, small ones in the axils of the upper leaves, and large ones 
in the axils of a few of the lower leaves of the spike. The micro- 
spores are borne in the smaller spore-cases and the macrospores 
in the larger ones. Figures 241-243 give the details. There 
are many microspores in a single small spore -case, but 3-4 ma- 
crospores in a large spore-case. 

394. Male prothallia. — The prothallia of selaginellaare much 
reduced structures. The microspores when mature are already 
divided into two cells. When they grow into the mature pro- 
thallium a few more cells are formed, and some of the inner ones 
form the spermatozoids, as seen in fig. 244. Here we see that 




Fig. 244. 
Details of microspore and male prothallium of selaginella ; ist, microspore : 2d, wall re- 
moved to show small prothallial cell below ; 3d, mature male prothallium still within the 
wall ; 4th, small cell below is the prothallial cell, the remainder is antheridium with wall and 
three sperm cells within ; 5th spermatozoid. After Beliaieff and Pfeffer. 

the antheridium itself is larger than the prothallia. Only an- 
theridia are developed on the prothallia formed from the 
microspores, and for this reason the prothallia are called male 
prothallia. In fact a male prothallium of selaginella is nearly 
all antheridium, so reduced has the gametophyte become here. 

395. Female prothallia. — The female prothallia are devel- 
oped from the macrospores. The macrospores when mature have 
a rough, thick, hard wall. The female prothallium begins to 
develop inside of the macrospore before it leaves the sporangium. 
The protoplasm is richer near the wall of the spore and at the 



LITTLE CI. IB MOSSES. 



195 



upper end. Here the nucleus divides a great many times, and 
finally cell walls are formed, so that a tissue of considerable ex- 
tent is formed inside the wall of the spore, which is very 
different from what takes place in the ferns we have 
studied. As the prothallium matures the spore is cracked 
at the point where the three angles meet, as shown in 
fig. 246. The archegonia are developed in this exposed 
surface, and several can be seen in the illustration. 

396. Embyro. — After fertilization the egg divides in such a way 
that a long cell called a suspensor is cut off from the upper side, 






Fig. 245. Fig. 246. 

Section of mature macrospore Mature female prothallium of * l S- 2 47- 

of selagmella. showing female selaginella, just bursting open Seedling of sela- 

prothallium and archegonia. the wall of macrospore, exposing ginella still attached 
After Pfeffer. archegonia. After Pfeffer. to the macrospore. 

After Campbell. 

which elongates and pushes the developing embyro down into the center of 
the spore, or what is now the female prothallium. Here it derives nourish- 
ment from the tissues of the prothallium, and eventually the root and stem 
emerge, while a process called the " foot " is still attached to the prothallium. 
When the root takes hold on the soil the embyro becomes free. 



CHAPTER XXIX. 

QUILLWORTS (ISOETES). 

397. The quillworts, as they 
are popularly called, are very 
curious plants. They grow in 
wet marshy places. They receive 
their name from the supposed 
resemblance of the leaf to a quill. 
Fig. 248 represents one of these 
quillworts (Isoetes engelmannii). 
The leaves are the prominent 
part of the plant, and they are 
about all that can be seen except 
the roots, without removing the 
leaves. Each leaf, it will be 
seen, is long and needle-like, ex- 
cept the basal part, which is 
expanded, not very unlike, in out- 
line, a scale of an onion. These 
expanded basal portions of the 
leaves closely overlap each other, 
and the very short stem is com- 
pletely covered at all times. Fig. 
250 is from a longitudinal sec- 
tion of a quillwort. It shows 
the form of the leaves from this 
view (side view), and also the 
mature plant, sporophyi general outline of the short stem, 

The stem is therefore a very short object. 

196 







which is triangular 



QU1LLW0RTS. 



197 



398. Sporangia of isocces. — If we pull off some of the 
leaves of the plant we see that they are somewhat spoon-shaped 
as in fig. 249. In the inner surface of the expanded base we 
note a circular depression which seems to be of a different text 





Fig. 249. 

Base of leaf of isoetes, 
showing sporangium with 
macrospores. (Isoetes en- 
gelmannii.) 



Fig. 250. 
Section of plant of Isoetes engelmanii, showing cup- 
shaped stem, and longitudinal sections of the sporan- 
gia in the thickened bases of the leaves. 



ure from the other portions of the leaf. This is a sporangium. 
Beside the spores on the inside of the sporangium, there are 
strands of sterile tissue which extend across the cavity. This is 
peculiar to isoetes of all the members of the class of plants to 
which the ferns belong, but it will be remembered that sterile 
strands of tissue are found in some of the liverworts in the form 
of elaters. 

399. The spores of isoetes are of two kinds, small ones 
(microspores) and large ones (macrospores), so that in this 
respect it agrees with selaginella, though it is so very different in 
other respects. When one kind of >pore is borne in a sporan- 



198 MORPHOLOGY. 

gium usually all in that sporangium are of the same kind, so that 
certain sporangia bear microspores, and others bear macrospores. 
But it is not uncommon to find both kinds in the same sporan- 
gium. When a sporangium bears only microspores the number 
is much greater than when one bears only macrospores. 

400. If we examine some of the microspores of isoetes we see that they are 
shaped like the quarters of an apple, that is they are of the bilateral type as 
seen in some of the ferns (asplenium). 

401. Male prothallia. — In isoetes, as in selaginella, the microspores de- 
velop only male prothallia, and these are very rudimentary, one division of 
the spore having taken place before the spore is mature, just as in selagi- 
nella. 

402. Female prothallia. — These are developed from the macrospores. The 
latter are of the tetrahedral type. The development of the female prothal- 
lium takes place in much the same way as in selaginella, the entire prothal- 
lium being enclosed in the macrospore, though the cell divisions take place 
after it has left the sporangium. When the archegonia begin to develop 
the macrospore cracks at the three angles and the surface bearing the arche- 
gonia projects slightly as in selaginella. 

403. Embryo. — The embryo lies well immersed in the tissue of the pro- 
thallium, though there is no suspensor developed as in selaginella. 



CHAPTER XXX. 

COMPARISON OF FERNS AND THEIR RELATIVES. 

404. Comparison of selaginella and isoetes with the ferns. — On compar- 
ing selaginella and isoetes with the ferns, we see that the sporophvte is, as 
in the ferns, the prominent part of the plant. It possesses root, stem, and 
leaves. While these plants are not so large in size as some of the ferns, 
still we see that there has been a great advance in the sporophvte of selagi- 
nella and isoetes upon what exists in the ferns. There is a division of labor 
between the sporophylls. in which some of them bear microsporangia with 
microspores, and some bear macrosporangia with only macrospores. In the 
ferns and horsetails there is only one kind of sporophyll, sporangium, and 
spore in a species. By this division of labor, or differentiation, between the 
sporophylls, one kind of spore, the microspore, is compelled to form a male 
prothallium. while the other kind of spore, the macrospore, is compelled to 
form a female prothallium. This represents a progression of the sporophvte 
of a very important nature. 

405. On comparing the gametophyte of selaginella and isoetes with that 
of the ferns, we see that there has been a still farther retrogression in size 
from that which we found in the independent and large gametophyte of the 
liverworts and mosses. In the ferns, while it is reduced, it still forms 
rhizoids, and leads an independent life, absorbing its own nutrient materials, 
and assimilating carbon. In selaginella and isoetes the gametophyte does 
not escape from the spore, nor does it form absorbing organs, nor develop 
assimilative tissue. The reduced prothallium develops at the expense of 
food stored by the sporophyte while the spore is developing. Thus, while 
the gametophyte is separate from the sporophvte in selaginella and isoetes, 
it is really dependent on it for support or nourishment. 

406. The important general characters possessed by the ferns and their 
so-called allies, a- we have found, are as follows: The spore-bearing part. 
which i< the fern plant, lead- an independent existence from the prothallium. 
and forms root. stem, and leaves. The spores are borne in sporangia on 
th<- leave-. The prothallium also leads an independent existence, though in 
isoetes and selaginella it ha- become almost entirely dependent on the sporo- 

199 



200 



M0RPH0L0G Y. 



phyte. The prothallium bears also well -developed antheridia and arche- 
gonia. The root, stem, and leaves of the sporophyte possess vascular 
tissue. All the ferns and their allies agree in the possession of these char- 
acters. The mosses and liverworts have well-developed antheridia and 
archegonia, and the higher plants have vascular tissue. But no plant of 
either of these groups possesses the combined characters which we rind in 
the ferns and their relatives. The latter are. therefore, the fern-like plants, 
or pteridophyla. The living forms of the pteridophyta are classified as fol- 
lows into families or orders. 



407. 



Class I. Filicales. « 



Pteridophyta, 

Eusporangiatoe 



Leptosporangiatae. 



Class II. Equisetales. \ ^I^ be ? 



setaceae. 
setum) 



tt Ophioglossaceae. 

Homosporous. X ./ ,f. 

r j Marattiaceae. 

? Heterosporous (Isoetaceae (Isoetes). 

( Osmundaceae. 

Schizaeaceae. 

Gleicheniaceae. 

H y m e n o p h y 1- 

laceae. 

Cyatheaceae. 

Polypodiaceae. 

Polypodium, Ono- 

clea, Aspidium, 

[ etc. 

tt, ( Salviniaceae. 

Heterosporous. j Marsiliace£e . 



Homosporous. 



Class III. Lycopodiales. -j 



f tt Lycopodiaceae (Lvcopodium). 

f Homosporous. \ T -., f ,, v . - , / ' 

\ r Psilotaceae (tropical forms). 



[ Heterosporous. (Selaginellacese (Selaginella). 



COMPARISON OF PTERIDOPH VTA. 



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CHAPTER XXXI. 

GYM NOSPERMS. 
/ The white pine. 

409. General aspect of the white pine. — The white pine 
(Pinus strobus) is found in the Eastern United States. In 
favorable situations in the forest it reaches a height of about 50 
meters (about 160 feet), and the trunk a diameter of over 1 
meter. In well-formed trees the trunk is straight and towering; 
the branches where the sunlight has access and the trees are not 
crowded, or are young, reaching out in graceful arms, form a 
pyramidal outline to the tree. In old and dense forests the lower 
branches, because of lack of sunlight, have died away, leaving 
tall, bare trunks for a considerable height. 

410. The long shoots of the pine. — The branches are of- two kinds. Those 
which we readily recognize are the long branches, so called because the 
growth in length each year is considerable. The terminal bud of the long 
branches, as well as of the main stem, continues each year the growth of the 
main branch or shoot; while the lateral long branches arise each year from 
buds which are crowded close together around the base of the terminal bud. 
The lateral long branches of each year thus appear to be in a whorl. The 
distance between each false whorl of branches, then, represents one year's 
growth in length of the main stem or long branch. 

411. The dwarf shoots of the pine. — The dwarf branches arc all lateral 
on the long branches, or shoots. They are scattered over the year's growth, 
and each bears a cluster of five long, needle-shaped, green Leaves, which 
remain on the tree for several years. At the base of the green leaves are 
a number of chaff-like scales, the previous bud scales. While the dwarf 
branches thus bear green leaves, and scales, the long branches bear only 
thin scale-like leaves which are not green. 

202 



G YMNOSPERMS: WHITE PINE. 



203 



412. Spore-bearing leaves of the pine. — The two kinds of 
spore-bearing leaves of the pine, and their elose relatives, are 
so different from anything which we have yet studied, and are 
so unlike the green leaves o\ the pine, that we would scarcely 
recognize them as belonging to this category. Indeed there is 
great uncertainty regarding their origin. 

413. Male cones, or male flowers. — The male (ones are borne 
in clusters as shown in fig. 251. Each compact, nearly cylindri- 




Spray of white pine showing cluster of male cones just before the scattering of the pollen. 



<al, or conical moss is termed a cone, or flower, and each arises 
in place of a long lateral branch. One of these (ones is shown 



204 



MORPHOLOGY. 



considerably enlarged in fig. 252. The central axis of each 
cone is a lateral branch, and belongs to the stem series. The 
stem axis of the cone can be seen in fig. 253. It is completely 
covered by stout, thick, scale-like outgrowths. These scales 
are obovate in outline, and at the inner angle of the upper end 




Fig. 252. Fig. 253. Fig. 254. 

Staminate cone of white Section of staminate Two sporo- 

pine, with bud scales re- cone, showing sporangia, phylls removed, 
moved on one side. showing open- 

ing of sporangia. 

there are several rough, short spines. They are attached by 
their inner lower angle, which forms a short stalk or petiole, 
and continues through the inner face of the scale as a "mid- 
rib." What corresponds to the lamina of the scale-like leaf 
bulges out on each side below and makes the bulk of the scale. 
These prominences on the under side are the sporangia (micro- 
sporangia). There are thus two sporangia on a sporophyll 
(microsporophyll). When the spores (microspores), which 
here are usually called pollen grains, are mature each sporangium, 
or anther locule, splits down the middle as 
shown in fig. 254, and the spores are set free. 
414. Microspores of the pine, or pollen 

grains. — A mature pollen grain of the pine is 
Fig. 255. 
Pollen grain <>i shown in fig. 255. It is a queer-looking object, 
white pine. 

possessing on two sides an air sac, formed by the 

upheaval of the outer coat of the spore at these two points. 




GYMiXOSPEPMS : WHITE PINE. 



205 



When the pollen is mature, the moisture dries out of the scale 
(or stamen, as it is often called here) while 
it ripens. When a limb, bearing a (luster 
of male cones, is jarred by the hand, or by 
currents of air, the split suddenly opens, and 
a cloud of pollen bursts out from the numer- 
ous anther locules. The pollen is 
thus borne on the wind and some of 

it falls on the 

female flowers. 





Fig. 256. 
White pine, branch with cluster of 
mature cones shedding the seed. A 
few young cones four months old 
are shown on branch at the left. 
Drawn from photograph. 

415. Form of the ma- 
ture female cone. — A 

cluster of the white- 
pine cones is shown in 
fig. 256. These are 
mature, and the scales 
have spread as they do when mature and becoming dry, in 
order that the seeds may be set at liberty. The general out- 



F ig- 257- 
Mature cone of white pine 
at time of scattering of the 
seed, nearly natural size. 



?o6 



MORPHOLOGY. 



line of the cone is lanceolate, or long oval, and somewhat 
curved. It measures about \o-\$cm long. If we remove one 




Fig. 258. Fig. 259. Fig. 260. Fig. 261. Fig. 262. 

Sterile scale. Scale with Seeds have Back of scale Winged 

Seeds imdevel- we 11 -developed split off from with small cover seed free from 
oped. seeds. scale. scale. scale. 

Figs. 258-262. — White pine showing details of mature scales and seed. 

of the scales, just as they are beginning to spread, or before the 
seeds have scattered, we shall find the seeds at- 
tached to the upper surface at the lower end. 
There are two seeds on each scale, one at each 
lower angle. They are ovate in outline, and 
shaped somewhat like a biconvex lens. At this 
time the seeds easily fall away, and may be 
freed by jarring the cone. As the seed is 
detached from the scale a strip of tissue from 
the latter is peeled off. This forms a " wing " 
for the seed. It is attached to one end and is 
shaped something like a knife blade. On the 
back of the scale is a small appendage known 
as the cover scale. 

416. Formation of the female pine cone.— The female 
flowers begin their development rather late in the spring 
of the year. They are formed from terminal buds of 
the higher branches of the tree. In this way the cone 
may terminate the main shoot of a branch, or of the 
Fig, 2 r, 3 . lateral shoots in a whorl. After growth has proceeded 

Female (ones of the for some time in tin- spring, the terminal portion begins 

pine at tunc of pollina- 




I., 



assume the appearance (, t ;i young female cone or 



GYMNOSPERMS : WHITE FIXE. 



207 



flower. These young female cones, at about the time that the pollen is 
escaping from the anthers, are long ovate, measuring about 6-IO////;/ long. 
They stand upright as shown in fig. 263. 

417. Form of a " scale " of the female flower. — If we remove 
one of the scales from the cone at this stage we can better study 
it in detail. It is flattened, and oval in 
outline, with a stout " rib," if it may be so 
called, running through the middle line and 
terminating in a point. The scale is in 
two parts as shown in fig. 266, which is a 
view of the under side. The small "out- 
growth" which appears as an appendage is 
the cover scale, for while it is smaller in the 
pine than the other portion, in some of 
the relatives of the pine it is larger than its 
mate, and being on the outside, covers it. 
(The inner scale is sometimes called the ovu- 
liferous scale, because it bears the ovules. ) 
418. Ovules, or macrosporangia, of the 
lh V JiP\ pine. — At each of the lower angles of the 



1 





Kg. 264. 
Section of female cone 
of white pine, showing 
young ovules (macrospo- 
rangia 1 at base of the ovu- 
liferous scales. 



Fig. 265. 
Scale of white pine with the 
two ovules at base of ovulif- 
erous scale. 



Fig. 266. 
Scale of white pine seen 
from the outside, showing the 
cover scale. 



scale is a curious oval body with two curved, forceps-like pro- 
cesses at the lower and smaller end. These are the macro- 
sporangia, or, as they are, called in the higher plants, the ovules. 
These ovules, as we see, are in the positions of the seeds on the 



208 



MORPHOLOG Y. 



mature cones. In fact the wall of the ovule forms the outer coat 
of the seed, as we will later see. 

419. Pollination. — At the time when the pollen is mature the 
female cones are still erect on the branches, and the scales, which 
during the earlier stages of growth were closely pressed against 
one another around the axis, are now 
spread apart. As the clouds of pollen 
burst from the clusters of the male cones, 
some of it is wafted by the wind to the 
female cones. It is here caught in the 
open scales, and rolls down to their bases, 
where some of it falls between these 
forceps-like processes at the 
lower end of the ovule. At 




Fig. 267. 
Branch of white pine showing young female cones at time of pollination on the ends of 
the branches, and one-year-old cones below, near the time of fertilization. 

this time the ovule lias exuded a drop of a sticky fluid in this 
depression between the curved processes at its lower end. The 
pollen sticks to this, and later, as this viscid substance dries up, 
it pulls the pollen close up in the depression against the lower 



GYMNOSPEPMS : WHITE PINE. 



209 



end of the ovule. This depression is thus known as the pollen 
chamber. 

420. Now the open scales on the young female cone close up 
again, so tightly that water from rains is excluded. What is also 
very curious, the cones, which up to this 
time have been standing erect, so that 
the open scale could catch the pollen, 
now turn so that they hang downward. 
This more certainly excludes the rains, 
since the overlapping of the scales forms 
a shingled surface. Quantities of resin 
are also formed in the scales, which 
exudes and makes the cone practically 
impervious to water. 

421. The female cone now slowly 
grows during the summer and autumn, 
increasing but little in size during this 
time. During the winter it rests, that 
is, ceases to grow. With the coming of 
spring, growth commences again and 
at an accelerated rate. The increase in 
size is more rapid. The cone reaches 
maturity in September. We thus see 
that nearly eighteen months elapse from 
the beginning of the female flower to the maturity of the 
cone, and about fifteen months from the time that pollination 
takes place. 

422. Female prothallium of the pine. — To study this we must make careful 
longitudinal sections through the ovule (better made with the aid of a micro- 
tome). wSuch a section is shown in fig. 269. The outer layer of tissue, which 
at the upper end (point where the scale is attached to the axis of the cone) 
stands free, is the ovular coat, or integument. Within this integument, near 
the upper end, there is a cone-shaped mass of tissue, which farther down 
continues along next the integument in a thinner strip. This mass of tissue 
is the nucellus, or the 7nacro sporangium proper. The elliptical mass of tissue 
within this, shown in fig. 271 is the female prothallium. or what is usually 
here called the endosperm. The conical portion of the nucellus fits over the 




Fig. 268. 
Macrosporangium of pine 
(ovule), int, integument ; n, nu- 
cellus; ;;/, macrospore. (After 
Hoffmeister.) 



2IO 



MORPHOLOGY. 



prothallium, and is called the nucellar cap. Only one end of the endosperm 

(prothallium) is shown in fig. 271. 

423. Archegonia. — In the upper end of the endosperm (prothallium) are 

several archegonia, and they aid us in determining what portion is the female 

prothallium. The nucellus is of 

course formed before the prothallium. 
The latter arises from a cell (macro- 
spore) near the center of the nucellus. 
This cell is larger, and has a larger 
nucleus than its fellows (see fig. 268). 
The prothallium here is formed much 
in the same way as in selaginella, 
where we recollect it begins to de- 
velop before the macrospore has 





Fig. 269. Fig. 270. 

Section of ovule of white pine, int, integ- Upper portion of nucellus of white pine, 

ument; A- pollen chamber; />/, pollen tube; A', pollen-grain remains ; spc, sperm cells; 

«, nucellus; m, macrospore cavity. vn, vegetative nucleus; //, pollen tube. 

reached its full size, and where the archegonia begin to form before it Leaves 
the macrosporangium. 

421. Male prcthallia. T>y the time the pollen is mature the male pro- 
thallum is already partly formed. In fig. 255 we can see two well-formed 
cells. Other cells are said to be formed earlier, but they become so flattened 
that it IS difficult to make them out when the pollen grain is mature. At this 
Mage of development tin- pollen grain is lodged at the mouth of the ovule. 
and i> drawn up into the pollen chamber. 

425. Farther growth of the male prothallium. During the summer and 
autumn the male prothallium makes some farther growth, but this is slow. 
The larger cell, called the vegetative cell, elongates by the*formation of a 
tube, forming a sac, known a- the pollen tube. Itiseither simple or branched, 
[nside of this sac the cell- of the prothallium are protected, and farther 



GYMA 7 OS TERMS : WHITE TINE. 



211 



division of the cells takes place here, jusl as the female prothallium develops 
in the cavity of the nucellus, from the macrospore. The nucleus of the vege- 
tative cell passes down the cavity of this 
tubular sac. The antherid cell, which is the 
smaller cell of the pollen grain, in the pine, 
divides by a cross wall into a so-called stalk 
cell, and a mother sperm cell, the latter 
corresponding to the central cell of the an- rPx/i^^SS^r^ Ry&sk*^ S & 




Fig. 271. 
Section through upper part of nucellus and 
endosperm of white pine, showing upper por- 
tion of archegonium, the entering sperm cells, 
and track of pollen tube ; nc, nucellus : fit, 
pollen tube ; sfic, sperm cells. 




^AreH 



Fig. 272. 
Last division of the egg in the white 
pine cutting off the ventral canal cell 
at the apex of the archegonium. End, 
endosperm; Arch, archegonium. 



theridium. there being no wall formed. The sperm mother cell also passes 
down the tubular sac, and divides again into two sperm cells, as shown in 
fig. 270. About this time, or rather a little earlier, with the pollen tube part 
way through the nucellar cap, winter overtakes it, and all growth ceases 
until the following spring. 

426. Fertilization. — In the spring the advance of the pollen tube con- 
tinues, and it finally passes through the nucellar cap about the time that the 
archegonia are formed and the egg cell is mature, as shown in fig. 271. The 
pollen tube now opens and the sperm cells escape into the archegonium, and 
later one of them fuses with the Qgg nucleus. The fertilized egg is now 
ready to develop into the embryo pine. 

427. Homology of the parts of the female cone. — Opinions are divided as 
to the homology of the parts of the female cone of the pine. Some consider 

entire cone to be homologous with a flower of the angiosperms. The en- 



212 



MORPHOLOGY. 



tire scale according to this view is a carpel, or sporophyll, which is divided 
into the cover scale and the ovuliferous scale. This division of the sporophyll 
is considered similar to that which we have in isoetes, where the sporophyll 




*W 



t'tm 








Fig. 273. 
Archegonium of Picea 
vulgaris, sperm cell ap- 
proaching the nucleus of 
egg cell. 



Fig. 274. 
Archegonium of Picea 
vulgaris showing fusion 
of sperm nucleus with 
egg nucleus. 



Fig. 275. 
Embryo of 
white pine re- 
moved from 
seed, showing 
several coty- 
ledons. 



Fig. 276. 
Pine seedling just 
emerging 
ground. 



from the 



Figs. 273, 274. — Fertilization in picea. (After Strasburger.) 

has a ligule above the sporangium, or as in ophioglossum, where the leaf is 
divided into a fertile and a sterile portion. 

A more recent view regards each cone scale as a flower, the ovuliferous 
scale composed of three united carpels arising in the axil of a Leaf, the cover 
scale. Two of the carpels are reduced to ovules, and the outer integument 
is expanded into the lateral portion of the scale, while the central carpel is 
sterile and ends in the point or mucro of the scale. 



GYMNOSPERMS: WHITE PINE. 



213 










Fig. 277. 
White-pine seedling casting seed coats. 



CHAPTER XXXII. 



FURTHER STUDIES ON GYMNOSPERMS. 



Cycas. 



428. In such gymnosperms as cycas, illustrated in the front- 
ispiece, there is a close resemblance to the members of the fern 

group, especially the ferns themselves. 
This is at once suggested by the form of 
the leaves. The stem is short and thick. 
The leaves have a stout midrib and 
numerous narrow pinnae. In the center 
of this rosette of leaves are numerous 
smaller leaves, closely overlapping like 
bud scales. If we remove one of these 
at the time the fruit is forming we see that 
in general it conforms to the plan of the 
large leaves. There are a midrib and a 
number of narrow pinnae near the free 
end, the entire leaf being covered with 
woolly hairs. But at the lower end, in 
place of the pinnae, we see oval bodies. 
These are the macrosporangia (ovules) 

of cycas, and correspond to the macrosporangia of selaginella, 

and the leaf is the macrosporophyll. 

429. Female prothallium of cycas. — In figs. 279, 280 are 
shown mature ovules, or macrosporangia, of cycas. In 280, which 
is aroentgen-ray photograph of 279, the oval prothallium can be 
seen. So in cycas, as in selaginella, the female prothallium is 

214 




Fig. 278 
Macrosporophyll 
revoluta. 



of Cycas 



FURTHER STUDIES ON GYMNOSPERMS. 



215 



developed entirely inside of the macrosporangium, and derives 
the nutriment for its growth from the cycas plant, which is the 




Fig. 279. 
Macrosporangium ot Cycas revoluta 



Fig. 280. 

Roentgen photograph of same, show- 
ing female prothallium. 



sporophyte. Archegonia are developed in this internal mass of 
cells. This aids us in deter- 
mining that it is the prothal- 
lium. In cycas it is also called 
endosperm, just as in the 
pines. 



430. If we cut open one of the 
mature ovules, we can see the en- 
dosperm (prothallium) as a whitish 
mass of tissue. Immediately sur- 
rounding it at maturity is a thin, 
papery tissue, the remains of the 
nucellus (macrosporangium), and 
outside of this are the coats of the 
ovule, an outer fleshy one and an 
inner stony one. 

431. Microspores, or pollen, of 
cycas. — The cycas plant illustrated 
in the frontispiece is a female plant. 
Male plants also exist which have 




A sporophyl! 



hig. 281. 

stamen) of cycas ; sporangia in 



small leavM in th,> r,*nt,>r tW K M r « rou P s on the under , side - /'.group ot sporangia; 
small leaver in tne centei that bear c , open sporangia. (From Warming.) 



2ib 



MORPHOLOG Y. 



only microsporangia. These leaves, while they resemble the ordinary leaves, 
are smaller and correspond to the stamens. Upon 
the under side, as shown in fig. 281, the microspo- 
rangia are borne in groups of three or four, and these 
contain the microspores, or pollen grains. The ar- 
rangement of these microsporangia on the under side 
of the cycas leaves bears a strong resemblance to the 
arrangement of the sporangia on the under side of 
the leaves of some ferns. 

432. The gingko tree is 
another very interesting plant 
belonging to this same group. 
Tt is a relic of a genus which j Fig. 282. 

Zamia inte- 
grifolia,show- 
1 n g thick 
stem, fern-like 
leaves, and 
cone of male 
flowers. 

flourished in the remote 
past, and it is interesting 
also because of the re- 
semblance of the leaves 
to some of the ferns like 
adiantum, which sug- 
gests that this form of 
the leaf in gingko has 
^een inherited from some 
fern-like ancestor. 

433. While the resem- 
blance of the leaves of 
some of the gy mnosperms 
to those of the ferns sug- 
gests fern-like ancestors 
for the members of this 
group, there is stronger 
evidence of such ances- 
try in the fact that a pro- 
thallium can well be de- 

K " 3 " -i-i 1 

Two spermatozoids in end of pollen tube of cycas. (After termmed in tne ovules. 

drawing by Hirase and ikeno.) T l u . endbsperm with its 

well-formed archegonia is to be considered .1 prothallium. 

434. Spermatozoids in some gymnosperms. But within the past two 
year- it has been discovered in gingko, cycas, and zamia, all belonging to this 







FURTHER STUDIES ON GYMNOSPERMS. 2\J 



group, that the sperm cells are well-formed spermatozoids. In zamia each 
one is shaped somewhat like the half of a biconvex lens, and around the con- 
vex surface are several coils of cilia. Alter the 
pollen tube has grown down through the nucellus, 

and has reached a depression at the end of the 
prothallium (endosperm) where the archegonia 
are formed, the spermatozoids are set free from 
the pollen tube, swim around in a liquid in this 
depression, and later fuse with the egg. In 
gingko and cycas these spermatozoids were first 
discovered by Ikeno and Hirase in Japan, and 
later in zamia by Webber in this country. In 
figs. 283-286 the details of the male prothallia 
and of fertilization are shown. 

435. The sporophyte in the gymnosperms. — 
In the pollen grains of the gymnosperms we 
easily recognize the characters belonging to the 
spores in the ferns and their allies, as well as in 
the liverworts and mosses. Thev belong to the 




Fig. 284. 

Fertilization in cycas, small 

spermatozoid fusing with the 

same series of organs, are borne on the same larger female nucleus of the egg. 

, • r i i i • The e SS protoplasm fills the 

phase or generation of the plant, and are practi- archegonium. (From drawings 

"y formed in the same general way, the by Hirase and Ikeno) 



cally formed in the same general way, 

variations between the different groups not being greater than those within 

a single group. 

the sporophyte. 




These spores we have recognized as being the product of 
We are able then to identify the sporophyte as that phase or 
generation of the plant formed from the fertilized 
egg and bearing ultimately the spores. We see 
from this that the sporophyte in the gymnosperms 
is the prominent part of the plant, just as we 
found it to be in the ferns. The pine tree, then, 
as well as the gingko, cycas, yew, hemlock- 
spruce, black spruce, the giant redwood of Cali- 
fornia, etc., are sporophytes. 

While the sporangia (anther sacs) of the male 
flowers open and permit the spores (pollen) to be scattered, the sporangia of the 
female flowers of the gymnosperms rarely open. The macrospore is developed 
within sporangium (nucellus) to form the female prothallium (endosperm). 

436 The gametophyte has become dependent on the sporophyte. — In this 
respect the gymnosperms differ widely from the pteridophytes, though we see 
suggestions of this condition of things in isoetes and selaginella, where the 
female prothallium is developed within the macrospore, and even in sela- 
ginella begins, and nearly completes, its development while still in the spo- 
rangium. 



Fig. 285. 
.Spermatozoid of gingko. show- 
ing cilia at one end and tail at 
the other (After drawings by 
Hirase and Ikeno.) 



218 



MORPHOLOG V. 




In comparing the female prothallium of the gymnosperms with that of the 
fern group we see a remarkable change has taken place. The female pro- 
thallium of the gymno- 
Ex ? 2 r> sperms is very much 

A S ! reduced in size. Espe- 

cially, it no longer leads 
an independent existence 
from the sporophyte, as 
is the case with nearly 
all the fern group. It 
remains enclosed within 
the macrosporangium (in 
cycas if not fertilized it 
sometimes grows outside 
of the macrosporangium 
and becomes green), and 
derives its nourishment 
through it from the sporo- 
phyte, to which the latter 
remains organically con- 
nected. This condition 
of the female prothallium 
of the gymnosperms 
necessitated a special 

Gingko biloba. A, mature pollen grain ;/?, germinating adaptation of the male 

pollen grain, the branched tube entering among the cells ^vofh-llinm ; n order tint 

of the nucellus; Ex, exine (outer wall of spore); /\, pro- piomainum in oraei mac 

thallial cell ; /\ 2 , antheridial cell (divides later to form stalk the sperm cells may reach 
cell and generative cell) ; P %t vegetative cell ; Va, vacuoles ; . 

Nc t nucellus. (After drawings by Hirase and Ikeno.) and fertilize the egg cell. 




Fig. 287. 

Gingko biloba, diagrammatic representation of the relation of pollen tube to the arche- 
gonium in the end of the nucellus. pt } pollen tube; 0, archegonium. (Alter drawing by 

and Ikeno.) 



437. Gymnosperms are naked seed plants. — The pine, as we have seen, 

naked seeds. That is, the seeds are not enclosed within the carpel, but 



FURTHER STUDIES ON GYMNOSPERMS. 



2IQ 



are exposed on the outer surface. All the plants of the great group to 

which the pine belongs have 

naked seeds. For this reason 

the name " gymnosperms " 

has been given to this great 

group. 

438. Classification of gymno- 
sperms. — The gingko tree has 
until recently been placed with 
the pines, yew, etc., in the class 
coniferee, but the discovery of 
the spermatozoids in the pollen 
tube suggests that it is not 
closely allied with the coniferae, 
and that it represents a class 
coordinate with them. Engler arranges the living gymnosperms as follows : 




Fig. 288. 
Spermatozoids of 
zamia in pollen tube 
j>g, pollen grain; «, a, 
spermatozoids. (After 
Webber.) 



Fig. 289. 
Spermatozoidof zamia 
showing spiral row of 
cilia. (After Webber.) 



Class 1. 
Class 2. 
Class 3. 



Class 4. Gnetales. 



Cycadales ; family Cycadaceae. Cycas, zamia, etc. 
Gingkoales ; family Gingkoaceae. Gingko. 

Coniferae ; family I. Taxaceae. Taxus, the common yew in the 
eastern United States, and Torreya, in the 
western United States, are examples, 
family 2. Pinaceae. Araucaria (redwood of California), 

firs, spruces, pines, cedars, cypress, etc. 
Welwitschia mirabilis, deserts of southwest Africa ; 
Ephedra, deserts of the Mediterranean and of West 
Asia. Gnetum, climbers (Lianas), from tropical Asia 
and America. 



220 



MORPIIOLOG Y. 



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CHAPTER XXXIII. 

MORPHOLOGY OF THE ANGIOSPERMS : TRILLIUM; 

DENTARIA. 

Trillium. 

440. General appearance. — As one of the plants to illustrate 
this group we may take the wake-robin, as it is sometimes called, 
or trillium. There are several species of this genus in the 
United States; the commonest one in the eastern part is the 
"white wake-robin" (Trillium grandiflorum). This occurs in 
or near the woods. A picture of the plant is shown in fig. 290. 
There is a thick, fleshy, underground stem, or rhizome as it is 
usually called. This rhizome is perennial, and is marked by 
ridges and scars. The roots are quite stout and possess coarse 
wrinkles. From the growing end of the rhizome each year the 
leafy, flowering stem arises. This is 20-^ocm (8-12 inches) in 
height. Near the upper end is a whorl of three ovate leaves, 
and from the center of this rosette rises the flower stalk, bearing 
the flower at its summit. 

441. Parts of the flower. Calyx. — Now if we examine the 
flower we will see that there are several leaf-like structures. 
These are arranged also in threes just as are the leaves. First 
there is a whorl of three, pointed, lanceolate, green, leaf-like 
members, which make up the calyx in the higher plants, and the 
parts of the calyx are sepals, that is, each leaf-like member is a 
sepal. But while the sepals are part of the flower, so called, we 
easily recognize them as belonging to the leaf series. 

221 



MORPHOLOG V. 
442. Corolla. — Next above the calyx is a whorl of white or 




pinkish members, in 
are also leaf-like in form, 

being usually somewhat 
make up what is the 
and each member o( the 

they are parts o\ the 
their form and posi- 

also belong to the leaf 

443. Androecium. — 

tion o\ the corolla is 

of members which do not 
form. They are known 
As seen in fig, 201 each 
ament ', and extending 
greater part of the length 
side. This part o\ the 
ridges form the anther 
Soon after the Sower is 
ther sacs open also by a 

along the edge o\ the 

time we see quantities o( 
or dust escaping from the 



I 



Trillium granditlorum, which 
and broader than the sepals, 
broader at the free end. These 
corolla in the higher plants, 
corolla is a petal, But while 
flower, and are not green, 
tion would suggest that they 
series. 

Within and above the inser- 
found another tier, or whorl, 
at first sight resemble leaves in 
in the higher plants as stamens, 
stamen possesses a stalk (= fil- 
along on cither side for the 
are four ridges, two on each 
stamen is the anther, and the 
sacs, or lobes, 
opened, these an- 
split in the wall 
ridge. At this 

yellowish powder 
ruptured anther 




Fig, 190. 
Trillium grandiflorum 



locules. If we place some of this under the microscope we see 



ANGIOSPERMS: TRILLIUM, 



223 



that it is made up of minute bodies which resemble spores; they 



are rounded in form, and the outer wal 




is spin\'. They are in faet 
spores, the microspores 
of the trillium, and here, 
as in the gymnosperms, 

are better known as pollen. 




Fig. 291. 
Sepal, petal, stamen, and pistil of Trillium 
grandi riorum. 



444. The stamen a sporo- 
phyll. — Since these pollen 
grains are the spores, we would 
infer, from what we have 
learned of the ferns and gym- 
nosperms, that this member of 
the flower which bears them is a sporophyll ; 
and this is the case. It is in fact what is called 
the micro sporophyll. Then we see also that the 
anther sacs, since they enclose the spores, would 
be the sporangia (microsporangia). From this 
it is now quite clear that the stamens 
belong also to the leaf series. They 
are just six in number, twice the number 
found in a whorl of leaves, or sepals, 
or corolla. It is believed, therefore, 
that there are two whorls of stamens in the flower of trillium. 

445. Gynoecium. — Next above the stamens and at the center 
of the flower is a stout, angular, ovate body which terminates in 
three long, slender, curved points. This is the pistil, and at 




Fig. 292. 
Trillium gran- 
dirlorum, with 
the compound 
pistil expanded 
into three leaf- 
like members. 
At the right 
these three are 
shown in detail. 



224 



MORPHOLOGY. 



present the only suggestion which it gives of belonging to the 
leaf series is the fact that the end is divided into three parts, the 
number of parts in each successive whorl of members of the 
flower. If we cut across the body of this pistil and examine it 
with a low power we see that there are three chambers or cavi- 
ties, and at the junction of each 
the walls suggest to us that this 
body may have been formed by the *. 
infolding of the margins of three 
leaf-like members, the places of < 
contact having then become grown 
together. We see also that from 
the incurved 



margins of each 

division of the 

pistil there stand 

out in the cav 

These are the ovules. No 

ovules we have learned fr< 

study of the gymnosperms 

sporangia (here the macrosporangia 





Fig. 293. 

Abnormal 
trillium. The 
nine parts of 
the perianth 
are green, 
and the outer 
whorls of 
stamens are 
expanded into 
petal -like 
members. 

is made up 



It is now more evident that this curious body, the pisti 
of three leaf-like members which have fused together, each mem- 
ber being the equivalent of a sporophyll (here the mac rosporo- 
phyll). This must be a fascinating observation, that 
plants of such widely different groups and of such 
different grades of complexity should have members 
formed on the same plan and belonging to the same 
series of members, devoted to similar functions, and 
yet carried out with such great modifications that at 
first we do not see this common meeting ground 
which a comparative study brings out so clearly. 

446. Transformations of the flower of trillium. — 
If anything more were needed to make it clear that 
the parts of the (lower of trillium belong to the leaf 
series we could obtain evidence from the transformations which 







Fig 204. 

Transformed 

stamen of tril- 
lium Bhowing 
anther locules 
on the margin. 






ANGIOSPERMS : DENTARIA. 225 

the flower of trillium sometimes presents. In fig. 293 is a sketch 
of a flower of trillium, made from a photograph. One set of 
the stamens has expanded into petal -like organs, with the anther 
sacs on the margin. In fig. 292 is shown a plant of Trillium 
grandi riorum in which the pistil has separated into three distinct 
and expanded leaf-like structures, all green except portions of 
the margin. 



Dentaria. 

447. General appearance. — For another study we may take 
a plant which belongs to another division of the higher plants, 
the common "pepper root," or " toothwort " (Dentaria 
diphylla) as it is sometimes called. This plant occurs in moist 
woods during the month of May, and is well distributed in the 
northeastern United States. A plant is shown in fig. 295. It 
has a creeping underground rhizome, whitish in color, fleshy, 
and with a few scales. Each spring the annual flower-bearing 
stem rises from one of the buds of the rhizome, and after the 
ripening of the seeds, dies down. 

The leaves are situated a little above the middle point of the 
stem. They are opposite and the number is two, each one 
being divided into three dentate lobes, making what is called a 
compound leaf. 

448. Parts of the flower. — The flowers are several, and they 
are borne on quite long stalks (pedicels) scattered over the ter- 
minal portion of the stem. We should now examine the parts 
of the flower beginning with the calyx. This we can see, look- 
ing at the under side of some of the flowers, possesses four scale- 
like sepals, which easily fall away after the opening of the flower. 
They do not resemble leaves so much as the sepals of trillium, 
but they belong to the leaf series, and there are two pairs in the 
set of four. The corolla also possesses four petals, which are more 
expanded than the sepals and are whitish in color. The sta- 
mens are six in number, one pair lower than the others, and also 



226 MORPHOLOC V. 

shorter. The filament is long in proportion to the anther, the 




latter consisting of two 
lobes or sacs, instead of 
four as in trillium. The 
pistil is composed of two 
carpels, or leaves fused 
together. So we find in 
the case of the pepper 
root that the parts of the 
flower are in twos, or 
multiples of two. Thus 
theyagreein this respect 
with the leaves ; and 
while w e do not see 

such a strong resem- 
blance between the 
parts of the flower 
here and the leaves, 

yet from the pres 
en< e of the pollen 



Fig. 
Toothwort ( Dentaria diphylla). 



ANGIOSPERMS : DENTARIA. 227 

(microspores) in the anther sacs (microsporangia) and of ovules 
(macrosporangia) on the margins of each half of the pistil, we 
are, from our previous studies, able to recognize here that all the 
members of the flower belong to the leaf series. 

449. In trillium and in the pepper root we have seen that the 
parts of the flower in each apparent whorl are either of the same 
number as the leaves in a whorl, or some multiple of that num- 
ber. This is true of a large number of other plants, but it is not 
true of all. A glance at the spring beauty (Claytonia virginiana, 
fig. 349) and at the anemone (or Isopyrum biternatum, fig. 355) 
will serve to show that the number of the different members of 
the flower may vary. The trillium and the dentaria were selected 
as being good examples to study first, to make it very clear that 
the members of the flower are fundamentally leaf structures, or 
rather that they belong to the same series of members as do the 
leaves of the plant. 



CHAPTER XXXIV. 

}AMETOPHYTE AND SPOROPHYTE OF ANGIO- 
SPERMS. 




450. Male prothallium of angiosperms. — The first division 
which takes place in the nucleus of the pollen grain occurs, in 
the case of trillium and many others of the angio- 
sperms, before the pollen grain is mature. In the 
case of some specimens of T. grandiflorum in 
which the pollen was formed during the month 

of October of the year before flowering, the divi- 

pig. 297. J ° 7 

Nearly mature sion of the nucleus into two nuclei took place 

pollen grain of tril- . 

Hum. The smaller soon alter the formation 01 the four cells from 

cell is the genera- . . 

tiveceii. the mother cell. Ihe nucleus divided in the 

young pollen grain is shown in fig. 297. After this takes 
place the wall of the pollen grain becomes stouter, and minute 
spiny projections are formed. 

451. The larger cell is the vegetative cell 

of the prothallium, while the smaller one, since 

it later forms the sperm cells, is the generative 

cell. This generative cell then corresponds 

to the central cell of the antheridium, and the 

vegetative cell perhaps corresponds to a wall 

cell of the antheridium. If this is so, then the Germinating spores 

male prothallium of angiosperms has become (pollen grains) oi pel- 

1 ° 1 tandra ; generative 

reduced to a very simple antheridium. The nucleus in <>ne undi- 

r . . . . r - .... vided, in other divided 

farther growth takes place alter fertilization, to form the two sperm 

In some plants tin- generative cell divides into n , uclei - ; vegetativenu- 

1 ° 1 lens in each Dear the 

the t\v<> sperm cells at the maturity of the pollen grain. 
pollen grain. In other cases the generative cell divides in tin- pollen tube 
after the germination <>f the pollen grain, for stud)- >>t' the pollen tube the 
pollen may lie germinated in a weak solution of sugar, or on the cut surface 

228 




GAMETOPHYTE AX J) SPOROPHYTE. 



229 



of pear fruit, the latter being kept in a moist chamber to prevent drying 
the surface. 

452. In the spring after flowering the pollen escapes from the anther sacs, 
and as a result of pollination is brought to rest on the stigma of the pistil. 
Here it germinates, as we saw that is it develops a long tube which makes 
its way down through the 
style, and in through the 
micropyle to the embryo sae. 
where, in accordance with 
what takes place in other 
plants examined, one of the 
sperm cells unites with the 
egg, and fertilization of the 
egg is the result. 



453. Macrospore and embyro sac. 

three pistils or carpels are united into 
taria the two carpels are also united 
carpel. Simple carpels are found in 
example in the ranunculacese, the 
bine, etc. These simple carpels bear a 





— In trillium the 
one, and in den- 
into one compound 
many plants, for 
buttercups, colum- 
greater resemblance 
to a leaf, the mar- 
gins of which are 
folded around so 
that they meet and 
enclose the ovules 
or sporangia. 

454. If we cut 
across the com- 
pound pistil of tril- 
lium we find that 
the infoldingsof the 
three pistils meet to 
form three partial 
partitions which 
extend nearly to the center, dividing off three spaces. In 
these spaces are the ovules which arc attached to the infolded 
margins. If we make cross sections of a pistil of the May- 




&& 






Fig. 299. 

Section of pistil of trillium, Fig. 300. 

showing position of ovules Mandrake (Podo- 
(macrosporangia . phyllum peltatum;. 



230 



MORPHOLOGY, 



apple (podophyllum) and through the ovules when they are 
quite young, we will find that the ovule has a structure like that 
shown in fig. 301. At w is a cell much larger than the surround- 
ing ones. This is the macrospore. The tissue surrounding it 
is called here the nucellus, but because it contains the macrospore 
it must be the macrosporangium. The two coats or integuments of 
the ovule are yet short and have not grown out over the end of 
the nucellus. This macrospore increases in size, forming first a 
cavity or sac in the nucellus, the embryo sac. The nucleus divides 




Fig. 301 
Young ovule (macrosporangium) of podophyllum 



stage of the macrospore ; i.int, inner integument ; 



nucellus containing the one-celled 
o.intf outer integument. 



■elled 



several times until eight are formed, four in the micropylar end 
of the embryo sac and four in the opposite end. In some plants 
it has been found that one nucleus from each group of four 
moves toward the middle of the embryo sac. Here they fuse to- 
gether to form one nucleus, the endosperm nucleus or definitive 
nucleus shown in fig. 302. One of the nuclei at the micropylar 
end is the egg, while the two smaller ones nearer the end are the 






GAMETOPHYTE AND SPOROPHYTE. 



231 



synergids. The egg cell is all that remains of the archegonium 
in this reduced prothallium. The three nuclei at the lower end 
are the antipodal cells. 




Fig. 302. 
Podophyllum peltatum, ovule containing mature embryo sac ; two synergids and egg at 
left, endosperm nucleus in center, three antipodal cells at right. 

455. Embryo sac is the young female prothallium. — In 

figures 303, 305 are shown the different stages in the develop- 
ment of the embryo sac in lilium. 
The embryo sac at this stage is 
the young female prothallium, and 
the egg is the only remnant of the 
female sexual organ, the arche- 
gonium, in this reduced gameto- 
phyte. 

456. Fertilization. — Before /i 
fertilization can take place the ' 
pollen must be conveyed from 

the anther tO the Stigma. (For Macrospore (one-celled stage) of lilium. 

the different methods of pollination see Part III.) When the 
pollen tube has reached the embryo sac, it opens and the sperm 
cell is emptied into the embryo sac near the egg. The sperm 
nucleus now enters the protoplasm surrounding the egg nucleus. 
The male nucleus is usually smaller than the female nucleus, and 
sometimes, as in the cotton plant, it grows to near or quite the 




Fig. 303. 



MORPHOLOGY. 



size of the female nucleus before the fusion of the two takes place. 

In figs. 306 and 307 are shown the entering pollen tube with 
the sperm nucleus, and the fusion of the male and female nuclei. 
457. Fertilization in plants is fundamentally the same as 
in animals. — In all the great groups of plants as represented by 
spirogyra, oedogonium, vaucheria, peronospora, ferns, gymno- 




Fig. 304, 
Two- ami four-celled stage of embryo-sac of lilium. 



The middle one shows di\ ision 



nuclei to form the four-celled stage. (.Easter lily.) 
sperms, and in the angiosperms, fertilization, as we have seen, 
consists in the fusion oi a male nucleus with a female nucleus. 
Fertilization, then, in plants is identical with that which takes 
place in animals. 

458. Embryo. — After fertilization the egg develops into a 
short row of cells, the suspensor of the embryo. At the free end 
the embyro develops. In figs. 309 and 310 is a young embryo 
of trillium. 

459. Endosperm, the mature female prothallium. — During 
the development o\ the embryo the endosperm nucleus divides 



GAMETOPHYTE AND SPOROPHYTE. 



233 



into a great many nuclei in a mass of protoplasm, and cell walls 
are formed separating them into cells. This mass of cells is the 
endosperm , and it surrounds the 
embryo. It is the mature female 
pro thallium ) belated in its growth 
in the angiosperms, usually de- 
veloping only when fertilization 
takes place, and its use has been 
assured. 

460. Seed. — As the embryo 





Fig. 30 



Fig. 306. 



Mature embryo sac (young pro- Section through nucellus and upper part of embryo 

thallium) of lilium. ///, micropylar sac of cotton at time of entrance of p.- lien tube. E, 

end; .V, synergids ; E % egg; Pn> egg: S, synergids: P t pollen tube with sperm cell in 

polar nuclei; Ant, antipodals, the end. (Duggar.) 
(Easter liiyj 



234 



MORPHOLOG Y. 



is developing it derives its nourishment from the endosperm (or 
in some cases perhaps from the nucellus). At the same time 




Fig. 307- 
Fertilization of cotton. pt, 
pollen tube ; Sn, synergids ; E, 
egg, with male and female nu- 
cleus fusing. (Duggar.) 




the integuments increase 
in extent and harden as 
the seed is formed. 

461. Perisperm. — In 
most plants the nuce llus is 
all consumed in the devel- 
opment of the endosperm, 
so that only minute frag- 
ments of disorganized cell 
walls remain next the in- 
ner integument. In some 
plants, however, (the water- 
lily family, the pepper „ ^ig. 308. 

J J 1 rr Diagrammatic section of ovary and ovule at time 

family, etc.,) a portion of of fertilization in angiosperm /, funicle of ovule ; 

J '/ x Hi nucellus; ;;/, micropyle ; o, antipodal cells or 

the nucellus remains in- embryo sac ; *, endosperm nucleus ; X-, egg cell and 

synergids ; ai, outer integument of ovule ; //, inner 
tact in the mature Seed, integument The track of the pollen tube is shown 

down through the style, walls of the ovary to the 
In Such Seeds the remain- micropylar end of the embryo sac. 

ing portion of the nucellus is the perisperm. 

462. Presence or absence of endosperm in the seed. — In 
many of the angiosperms all of the endosperm is consumed by 
the embryo during its growth in the formation of the seed. This 
is the case in the rose family, crucifers, composites, willows, oaks, 
legumes, etc., as in the acorn, the bean, pea and others. In 
some, as in the bean, a large part of the nutrient substance pass- 



GAMETOPHYTE AND SPOROPHYTE. 



235 



ing from the endosperm into the embryo is stored in the cotyle- 
dons for use during germination. In other plants the endosperm 




Fig. 309. Fig. 310. 

Section of one end of ovule of trillium, showing Embryo e n - 

young embryo in endosperm. larged. 

is not all consumed by the time the seed is mature. Examples of 
this kind are found in the buttercup family, the violet, lily, palm, 






Fig. 311. 
Seed of violet, external view, and 
section. The section shows the embryo 
lying in the endosperm. 



Fig. 312. 
Section of fruit of pepper (Piper 
nigrum), showing small embryo lying 
in a small quantity of whitish endo- 
sperm at one end, the perisperm oc- 
cupying the larger part of the interior, 
surrounded by pericarp. 



jack-in-the-pulpit, etc. Here the remaining endosperm in the 
seed is used as food by the embryo during germination. 

463. Sporophyte is prominent and highly developed. — In the angiosperms 
then, as we have seen from the plants already studied, the trillium, dentaria, 



23 > MOKPHOLOG Y. 

etc., are sporophytes, that is they represent the spore-bearing, or sporophytic, 
stage, hist as we found in the ease of the gymnosperms and ferns, this stage 
is the prominent one, and the one by which we characterize and recognize the 
plant. We see also that the plants of this group are still more highly special- 
ized and complex than the gymnosperms, just as they were more specialized 
and complex than the members of the fern group. From the very simple 
condition in which we possibly find the sporophyte in some of the alga: like 
spirogyra, vaucheria, and coleochajte, there has been a gradual increase in 
size, specialization of parts, and complexity of structure through the bryo- 
phytes, pteridophytes, and gymnosperms, up to the highest types of plant 
structure found in the angiosperms. Not only do we find that these changes 
have taken place, but we see that, from a condition of complete dependence of 
the spore-bearing stage on the sexual stage (gametophyte), as we find it in the 
liverworts and mosses, it first becomes free from the gametophyte in the mem- 
bers of the fern group, and is here able to lead an independent existence. 
The sporophyte, then, might be regarded as the modern phase of plant life, 
since it is that which has become and remains the prominent one in later 
times. 

464. The gametophyte once prominent has become degenerate. — On the 
other hand we can see that just as remarkable changes have come upon the 
other phase of plant life, the sexual stage, or gametophyte. There is reason 
to believe that the gametophyte was the stage of plant life which in early 
times existed almost to the exclusion of the sporophyte, since the characteristic 
thallus of the alga? is better adapted to an aquatic life than is the spore-bearing 
state of plants. At least, we now find in the plants of this group as well as in 
the liverworts, that the gametophyte is the prominent stage. When we reach the 
members of the fern group, and the sporophyte becomes independent, we find 
that the gametophyte is decreasing in size, in the higher members of the pteri- 
dophytes, the male pro thallium consisting of only a few cells, while the fe- 
male prothallium completes its development still within the spore wall. And 
in selaginella it is entirely dependent on the sporophyte lor nourishment. 

465. As we pass through the gymnosperms we find that the condition of 
things which existed in the bryophytes lias been reversed, and the gameto- 
phyte is now entirely dependent on the sporophyte for its nourishment, the 
female prothallium not even becoming lice from the sporangium, which remains 
attached to the sporophyte, while the remnant of a male prothallium, during 
the stage of its growth, receives nourishment from the tissues of the nucellus 
through which it bores its waj to the egg-cell. 

466. En the angiosperms this gradual degradation of the male and female 
prothallia has reached a climax in a one celled male prothallium with two 
sperm-cells, and in the embryo sac with no clearly recognizable traces of an 
archegonium to identify it as a female prothallium. The development of the 
endosperm subsequent, in most casosj to fertilization, providing nourishment 



CAMETOPHYTE AND SPOROPHYTE. 



237 



for the sporophytic embryo at one stage or another, is believed to be the last 
remnant of the female prothallium in plants. 

467. Synopsis of members of the sporophyte in angiosperms. 



1 1 igher plant. 
Sporophyte phase 
(01 modern phase). 



\ Root. 
J Shoot. 



j Stem. 
\ Leaf. 



I Foliage leaves. 
Perianth leaves. 
' Spore-bearing leaves 

with sporangia. 
I (Sporangia sometimes 

on shoot.) 



Flower. 



238 



MORPHOLOG Y. 



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CHAPTER XXXV. 



MORPHOLOGY OF THE NUCLEUS AND SIGNIFI- 
CANCE OF GAMETOPHYTE AND SPOROPHYTE. 

469. In the development of the spores of the liverworts, 
mosses, ferns, and their allies, as well as in the development of 
the microspores of the gymnosperms and angiosperms, we have 

observed that four spores are formed 
from a single mother cell. These 





Fig. 3i3- 
Forming spores in mother 
cells (Polypodium vulgare). 



Fig. 314- 
Spores just mature and wall of 
mother cell broken (Asplenium bul- 
biferum). 



mother cells are formed as a last division of the fertile 
tissue (archesporium) of the sporangium. In ordinary cell di- 
vision the nucleus always divides prior to the division of the cell. 
In many cases it is directly connected with the laying down of 
the dividing cell wall. 

470. Direct division, of the nucleus. — The nucleus divides in 
two different ways. On the one hand the process is very simple. 
The nucleus simply fragments, or cuts itself in two. This is 
direct division. 

471. Indirect division of the nucleus. — On the other hand 
very complicated phenomena precede and attend the division of 

239 



240 



MdRPHOLOGY. 



the nucleus, giving rise to a succession of nuclear figures presented 
by a definite but variable series of evolutions on the part of the 
nuclear substance. This is indirect division of the nucleus, or 
karyokinesis. Indirect division of the nucleus is the usual method, 
and it occurs in the normal growth and division of the cell. The 
nuclear figures which are formed in the division of the mother 
cell into the four spores are somewhat different from those 
occurring in vegetative division, but their study will serve to show 
the general character of the process. 

472. Chromatin and linin of the nucleus. — In figure 315 
is represented a pollen mother cell of the May-apple (podophyl- 




Fig- 3i5- 
Pollen mother cell 
of podophyllum, rest- 
ing nucleus. Chroma- 
tin forming a net- 
work. 

(Figures 315-317 after Mottier.) 



Fig. 316. 
Spirem stage of nucleus. 
#?•, nuclear cavity ; n, nu- 
cleolus ; S/>, spirem. 



Fig. 317. 
Forming spindle, 
threads from proto- 
plasm with several 
poles, roping the 
chromosomes up to 
nuclear plate. 



lum). The nucleus is in the resting stage. There is a network 
consisting of very delicate threads, the linin network. Upon 
this network are numerous small granules, and at the junction of 
the threads are distinct knots. The nucleolus is quite large and 
prominent. The numerous small granules upon the linin stain 
very deeply when treated with certain dyes used in differentiating 
the unclear structure. This deeply staining substance is the 
chromatin of the nucleus. 



GAMETOPHYTE AND SPOROPHYTE. 



241 



473. The chromatin skein. — One of the first nuclear figures 

in the preparatory stages of division is the chromatin skein or 
spirem. The chromatin substance unites to form this. The 
spirem is in the form of a narrow continuous ribbon, or band, 
woven into an irregular skein, or gnarl, as shown in figure 316. 
This band splits longitudinally into two narrow ones, and then 
each divides into a definite number of segments, about eight in 
the case of podophyllum. Sometimes the longitudinal splitting of 
the band appears to take place after the separation into the chro- 
matin segments. The segments remain in pairs until they separate 
at the nuclear plate. 

474. Chromosomes, nuclear plate, and nuclear spindle. — 
Each one of these rod-like chromatin segments is a chromosome. 




Fig. 318. 

Karyokinesis in pollen mother cells of podophyllum. At the left the spindle with the 
chromosomes separating at the nuclear plate ; in the middle figure the chromosomes have 
reached the poles of the spindle, and at the right the chromosomes are forming the daughter 
nuclei. (After Mottier.) 



The pairs of chromosomes arrange themselves in a median plane 
of the nucleus, radiating somewhat in a stellate fashion, forming 
the nuclear plate, or monaster. At the same time threads of the 
protoplasm ( kinoplasm) become arranged in the form of a spindle, 
the axis of which is perpendicular to the nuclear plate of chromo- 
somes, as shown in figure 318, at left. Each pair of chromosomes 
now separate in the line of the division of the original spirem, 
one chromosome of each pair going to one pole of the spindle, 



242 



MORPHOLOGY. 






Fig. 319. 
Different stages in the separation of 
U-shaped chromosomes at the nuclear plate 
Mottier ) In podophyllum. 



divided 
(After 



while the other chromosome of each pair goes to the opposite 

pole. The chromosomes here unite to form the daughter nuclei. 

Each of these nuclei now 
divide as shown in figure 
320 (whether the chromo- 
somes in this second divi- 
sion in the mother cell split 
longitudinally or divide 
transversely has not been 
definitely settled), and four 
nuclei are formed in the 
pollen mother cell. The 

protoplasm about each one of these four nuclei now surrounds 

itself with a wall and the spores are formed. 

The number of chromosomes usually the same in a given 

species throughout one phase of the plant. — In those plants 

which have been carefully studied, the number of chromosomes 

in the dividing nucleus has been found to be fairly constant in a 

given species, through all the divisions in that stage or phase 

of the plant, especially in the embryonic, or young growing 

parts. For example, in the 

prothallium, or gameto- 

phyte, of certain ferns, as 

osmunda, the number of 

chromosomes in the divid- 
ing nucleus is always twelve. 

So in the development of 

the pollen of lilium from 

the mother cells, and in the 

divisions of the antherid 

cell to form the generative 

cells or sperm cells, there 

are always twelve chromo 

somes so far as has been cin-onu,so.ncs at poles 

found. In the development of the egg of lilium from the 

macrospore there are also twelve chromosomes. 




Fig. 320. 
Second division of 
nuclei in pollen mother 

cell of podophyllum, 



Fig. 321. 
Chromosomes uniting 
at poles to form the 
nuclei of the four spores. 
(After Mottier.) 



CAMETOPHYTE AND SFOJWPHYTE. 



243 



When fertilization takes place the number of chromosomes 
is doubled in the embryo. — In the spermatozoid of osmunda 
then, as well as in the egg, since these are developed on the game- 
tophyte, there are twelve chromosomes each. The same is true 
in the sperm-cell (generative cell) of lilium, and also in the egg- 
cell. When these nuclei unite, as they do in fertilization, the 
paternal nucleus with the maternal nucleus, the number of chro- 
mosomes in the fertilized egg, if we take lilium as an example, 
is twenty-four instead of twelve; the number is doubled. The 
fertilized egg is the beginning of the sporophyte, as we have seen. 
Curiously throughout all the divisions of the nucleus in the em- 
bryonic tissues of the sporophyte, so far as has been determined, 
up to the formation of the mother cells of the spores, the number 
of chromosomes is usually the same 

475. Reduction of the number of chromosomes in the nu- 
cleus. — If there were no reduction in the number of chromosomes 




Fig. 322. 
Karyokinesis in sporophyte cells of podophyllum (twice the number of chromosomes 
here that are found in the dividing spore mother cells). 

at any point in the life cycle of plants, the number would thus 
become infinitely large. A reduction, however, does take place. 



244 MORPHOLOG V. 

This usually occurs, either in the mother cell of the spores or in 
the divisions of its nucleus, at the time the spores are formed. In 
the mother cells a sort of pseudo-reduction is effected by the 
chromatin band separating into one half the usual number of nu- 
clear segments. So that in lilium during the first division of the 
nucleus of the mother cell the chromatin band divides into twelve 
segments, instead of twenty-four as it has done throughout the 
sporophyte stage. So in podophyllum during the first division in 
the mother cell it separates into eight instead of into sixteen. 
Whether a qualitative reduction by transverse division of the 
spirem band, unaccompanied by a longitudinal splitting, takes 
place during the first or second karyokinesis is still in doubt. 

476. Significance of karyokinesis and reduction. — The pre- 
cision with which the chromatin substance of the nucleus is di- 
vided, when in the spirem stage, and later the halves of the 
chromosomes are distributed to the daughter nuclei, has led to the 
belief that this substance bears the hereditary qualities of the 
organism, and that these qualities are thus transmitted with cer- 
tainty to the offspring. In reduction not only is the original 
number of chromosomes restored, it is believed by some that 
there is also a qualitative reduction of the chromatin, i.e. that 
each of the four spores possesses different qualitative elements of 
the chromatin as a result of the reducing division of the nucleus 
during their formation. 

The increase in number of chromosomes in the nucleus occurs 
with the beginning of the sporophyte, and the numerical reduc- 
tion occurs at the beginning of the gametophyte stage. The 
full import of karyokinesis and reduction is perhaps not yet 
known, but there is little doubt that a profound significance is to 
be attached to these interesting phenomena in plant life. 

377. The gametophyte may develop directly from the tissue 
of the sporophyte. — [f portions of the sporophyte of certain of 
the mosses, as sections of a growing seta, or of the growing 
< apsule, be placed on a moist substratum, under favorable condi- 
tions some of the external cells will grow directly into protonemal 
threads. In some of the ferns, as iu the sensitive fern (onoclea), 



GAMETOPHYTE AND SPOROPHYTE. 



245 



when the fertile leaves are expanding into the sterile ones, proto- 
nemal outgrowths occur among the aborted sporangia on the 
Leaves of the sporophyte. Similar rudimentary protonemal 
growths sometimes occur on the leaves of the common brake 
(pteris) among the sporangia, and some of the rudimentary spo- 
rangia become changed into the protonema. In some other 
ferns, as in asplenium(A. filix-foemina, var. clarissiraa), prothallia 
are borne among the aborted sporangia, which bear antheridia 
and archegonia. In these cases the gametophyte develops from 
the tissue of the sporophyte without the intervention or necessity 
of the spores. This is apospory. 

478. The sporophyte may develop directly from the tissue 
of the gametophyte. — In some of the ferns, Pteris cretica for 
example, the embryo fern sporophyte arises directly from the tissue 
of the prothallium, without 
the intervention of sexual 
organs, and in some cases 
no sexual organs are de- 
veloped on such prothallia. 
Sexual organs, then, and 
the fusion of the spermato- 
zoid and Qgg nucleus are 
not here necessary for the 
development of the spo- 
rophyte. This is apogamy. 
Apogamy occurs in some 
other species of ferns, and 
in other groups of plants as well, though it is in general a rare 
occurrence except in certain species, where it may be the general 
rule. 

479. Perhaps there is not a fundamental difference between 
gametophyte and sporophyte. — This development of sporo- 
phyte, or leafy-stemmed plant of the fern, from the tissue of the 
gametophyte is taken by some to indicate that there is not such a 
great difference between the gametophyte and sporophyte of plants 
as others contend. In accordance with this view it has been 




Fig. 323- 
Apogamy in Pteris cretica. 



246 MORPHOLOG Y. 

suggested that the leafy-stemmed moss plant, as well as the leafy- 
stem of the liverworts, is homologous with the sporophyte or 
leafy stem of the fern plant; that it arises by budding from the 
protenema; and that the sexual organs are borne then on the 
sporophyte. 



LESSONS ON PLANT FAMILIES. 

CHAPTER XXXVI. 

RELATIONSHIPS SHOWN BY FLOWER AND FRUIT. 

480. Importance of the flower in showing kinships among 
the higher plants. — In the seed-bearing plants which we are now 
studying we cannot fail to be impressed with the general pres- 
ence of what is called the flower, and that the flower has its culmi- 
nating series in the spore-bearing members of the plant (stamens 
and carpels). Aside from the very interesting comparison of the 
changes which have taken place in passing from the simple and 
generalized sporophyte of the liverworts and mosses to the com- 
plex and specialized sporophyte of the higher plants, we should 
now seek to interpret the various kinds of aggregations of the 
spore-bearing members, here termed stamens and carpels. In 
the part of the book which deals with ecology we shall see how 
the grouping of these members of the plant is an advantage to it 
in the performance of those functions necessary for fruition. 

481. While the spore-bearing members, as well as the floral 
envelopes, are thus grouped into '' flowers," there is a great 
diversity in the number, arrangement, and interrelation of these 
members, as is suggested by our study of trillium and dentaria. 
And a farther examination of the flowers of different plants would 
reveal a surprising variety of plans. Nevertheless, if we com- 
pare the flower of trillium with that of a lily for example, or the 
flower or dentaria with that of the bitter-cress (cardamine), we 
shall at once be struck with the similarity in the plan of the 

247 



248 MORPHOLOG r. 

flower, and in the number and arrangement of its members. 
This suggests to us that there may be some kinship, or rela- 
tionship between the lily and trillium, and between the bitter- 
n-ess and toothwort. In fact it is through the interpretation of 
these different plans that we are able to read in the book of 
nature of the relationship of these plants. As we found in the 
case of the ferns that the most important characters of rela- 
tionship among genera and species are found among the spore- 
bearing leaves, so here the characters pertaining to the stamens 
and carpels are the principal guide posts, though the floral en- 
velopes are only second in importance, and leaves also frequently 
demand attention. 

Bearing these facts in mind, we can inquire of the plants 
themselves about some of the attributes of their families and 
tribes. 

NOTE FOR REFERENCE. 

482. Arrangement of flowers. — The arrangement of the flowers (inflores- 
cence) <m the stem is important in showing kinships. The flowers may be 
scattered and distant from each other on the plant, or they may be crowded 
close together in spikes, catkins, heads, etc. Many of the flower arrangements 
are dependent on the manner of the branching of the stem. Some of the 
systems of branching are as follows: 

483. I. DlCHOTOMOUS BRANCHING.- -True dichotomy (forking) does not 
occur in the shoots of flowering plants, but it does occur in some of the flower 
clusters. 

484. II. LATERAL BRANCHING. — Two main types. 

Monopodia! branching. — This occurs where the main shoot continues to 
grow more vigorously than the lateral branches which arise in succes- 
sion around the main stem. Examples in shoots, horse-chestnut, pines 
(see chapter on pine). Examples in flower clusters (from indetermi- 
nate inflorescence). 
Raceme; lateral axes unbranehed. youngest flowers mar the terminal 

portion of long main axis; ex. choke cherry, currant, etc. 
Spike; main a*is long, lateral unbranched axes with sessile and often 
crowded flowers; ex. plantain. Where the main axis is fleshy the 
spike forms &spadix^ as in skunk's cabbage, Indian turnip, etc.; if 
the spike falls away after maturity oi the flower or fruit it is a cat- 
kin or anient (willows, oak-. 1 



LESSONS ON PLANT FAMILIES. 249 

Umbel; the main axis is shortened, and the stalked flowers appear to 

form terminal clusters or whorls, as in the parsley, carrot, parsnip, 

etc. 
Head, or capitulum; the main axis is shortened and broadened, and 

bears sessile flowers, as in the sunflower, button-bush, etc. 
Panicle; when the raceme has the lateral axes branched it forms a 

panicle, as in the oat. When the panicle is flattened it forms a 

corymb. 
Sympodi a I branching or cymose branching. — The branches, or lateral 
axes, grow more vigorously than the main axis, and form for the 
time false axes (form cymes). 

1. Monochasium; only one lateral branch is produced from each rela- 
tive or false axis. 

Helicoid cyme; when the successive lateral branches always arise on 
the same side of the false axis, as in flower clusters of the forget- 
me-not. 

Scorpioid cyme; when the lateral branches arise alternately on op- 
posite sides of the false axis. 

2. Dichasium; each relative, or false, axis produces two branches* 
often forming a false dichotomy. Examples in shoots are found in 
the lilac, where the shoot appears to have a dichotomous branch- 
ing, though it is a false dichotomy. 

Forking cyme; flower cluster of chickweed. 

3. Pleiochasium; each relative, or false, axis produces more than two 
branches. 

485. The fruit. — The fruit of the angiosperms varies greatly, and often is 
greatly complicated. When the gyncecium is apocarpous (that is when the 
carpels are from the first distinct) the ripe carpels are separate, and. each is a 
fruit. In the syncarpous gyncecium (when the carpels are united) the fruit is 
more complicated, and still more so when other parts of the flower than 
the gyncecium remain united with it in the fruit. 

Pericarp; this is the part of the fruit which envelops the seed, and may 
consist of the carpels alone, or of the carpels and the adherent part of 
the receptacle, or calyx; it forms the wall of the fruit. 
Endocarp and exocarp. If the pericarp shows two different layers, or 
zones, of tissue, the outer is the exocarp, and the inner the endocarp, 
as in the cherry, peach, etc. 
Mesocarp; where there is an intermediate zone it is the mesocarp. 
I. Capsule (dry fruits). The capsule has a dry pericarp which opens 
(dehisces) at maturity. When the capsule is syncarpous the carpels may 
separate along the line of their union with each other longitudinally 
(septicidal dehiscence); or each carpel may split down the middle line 



250 MORPHOLOGY. 

[loculicidal dehiscence) as in fruit of iris; or the carpels may open by- 
pores {poricidal dehiscence}^ as in the poppy. 
Follicle; a capsule with a single carpel which dehisces along the ventral, 

or upper, suture [larkspur, peony). 
Legume ox pod; a capsule with a single carpel which dehisces along both 

sutures (pea, bean, etc.). 
Silique; a capsule of two carpels, which separate at maturity, leaving 

the partition wall persistent (toothwort, shepherd's-purse, and most 

others of the mustard family); when short it is a silicle or pouch. 
Pyxidium or pyxis; the capsule opens with a lid (plantain). 

II. Dry indehiscent fruits; do not dehisce or separate into distinct 
carpels. 

Nuts; with a dry, hard pericarp. 

Caryopsis; with one seed and a dry leathery pericarp (grasses). 
Achene; with pericarp adherent to the seed (sunflower and other com- 
posites. 

III. Schizocarp; a dry, several-loculed fruit, in which the carpels separate 
from each other at maturity but do not dehisce (umbelliferae, mallow). 

IV. Berry; endocarp and mesocarp 'both juicy (grape). 

V. Pome; mesocarp and outer portion of endocarp soft and juicy, inner 
portion of endocarp papery (apple). 

VI. Drupe, or stone fruit; endocarp hard and stony, exocarp soft and 
generally juicy (cherry, walnut); in the cocoanut the exocarp is soft 
and spongy. 



CHAPTER XXXVII. 



MONOCOTYLEDONS. 

Topic I : Monocotyledons with conspicuous petals 
(Petaloideae). 

Lesson I. Lily Family (Liliace^). 

CLASSIFICATION. 

486. Species. — It is not necessary for one to be a botanist in 
order to recognize, during a stroll in the woods where the tril- 
lium is flowering, that 
there are many individual 
plants very like each 
other. They may vary 
in size, and the parts 
may differ a little in 
form. When the flowers 
first open they are usually 
white, and in age they 
generally become pinkish. In some in- 
dividuals they are pinkish when they 
first open. Even with these variations, 
which are trifling in comparison with 
the points of close agreement, we recog- 
nize the individuals to be of the same 
kind, just as we recognize 
the corn plants grown 
from the seed of an ear of - 
corn as of the same kind. 
Individuals of the same 
kind, in this sense, form a species. The white wake-robin, then, 
is a species. 

251 




Fig. 324. 
Trillium erec- 
tum( purple form), 
two plants from 
one root-stock. 



252 MONOCO T YLEDONS. 

But there are other trilliums which differ greatly from this one. 
The purple trillium (T. erectum) shown in fig. 324 is very dif- 
ferent from it. So are a number of others. But the purple 
trillium is a species. It is made up of individuals variable, yet 
very like one another, more so than any one of them is like the 
white wake -robin. 

487. Genus. — Yet if we study all parts of the plant, the per- 
ennial root stock, the annual shoot, and the parts of the flower, 
we find a great resemblance. In this respect we find that there 
are several species which possess the same general characters. 
In other words, there is a relationship between these different 
species, a relationship which includes more than the individuals 
of one kind. It includes several kinds. Obviously, then, this 
is a relationship with broader limits, and of a higher grade, 
than that of the individuals of a species. The grade next higher 
than species we call genus. Trillium, then, is a genus. Briefly 
the characters of the genus trillium are as follows. 

488. Genus trillium. — Perianth of six parts : sepals 3, her- 
baceous, persistent ; petals colored. Stamens 6 (in two whorls), 
anthers opening inward. Ovary 3-loculed, 3-6 -angled ; stig- 
mas 3, slender, spreading. Herbs with a stout perennial root- 
stock with fleshy scale-like leaves, from which the low annual 
shoot arises bearing a terminal flower, and 3 large netted-veined 
leaves in a whorl. 

Note. — In speaking of the genus the present usage is to say 
trillium, but two words are usually employed in speaking of the 
species, as Trillium grandi riorum, T. erectum, etc. 

489. Genus erythronium. — The yellow adder-tongue, or 
dog-tooth violet (Erythronium americanum), shown in fig. 325, 
is quite different from any species of trillium. It differs more 
from any of the species of trillium than they do from each other. 
The perianth is of six parts, light yellow, often spotted near the 
base. Stamens are 6. The ovary is obovate, tapering at the 
base, 3-valved, seeds rather numerous, and the style is elongated. 
The flower stem, or scape, arises from a scaly bulb deep in the 
soil, and is sheathed by two elliptical-lanceolate, mottled leaves. 



PLANT FAMILIES: LILIACEjE. 



253 



The smaller plants have no flower and but one leaf, while the 
bulb is nearer the 
surface. Each year 
new bulbs are form- 
ed at the end of run- 
ners from a parent 
bulb. These run- 
ners penetrate each 
year deeper in the 
soil. The deeper 
bulbs bear the flow- 
er stems. 

490. Genus lili- 
um. — While the lily 
differs from either 
the trillium or ery- 
thronium, yet we 
recognize a rela- 
tionship when we 
compare the peri- 
anth of six colored 
parts, the 6 stamens, 
and the 3 -sided and 
long 
ovary. 

491. Family liliaceae. — The relationship between genera, as 
between trillium, erythronium, and lilium, brings us to a still 
higher order of relationship where the limits are broader than in 
the genus. Genera which are thus related make up the family. 
In the case of these genera the family has been named after the 
lily, and is the lily family, or Liliacece. This grouping of plants 
into species, genera, families, etc., according to characters and 
relationships is classification, or taxonomy. 

The lily family is a large one. Another example is found in 
the " Solomon* s-seal," with its elongated, perennial root-stock, 
the scars formed by the falling away of each annual shoot resem- 




Fig. 325- 
Adder-tongue (erythronium). At left belowf pistil, and three 
3 - lOCUleQ stamens opposite three parts of the perianth. Bulb at the 
right. 



254 MO NO COT YLED OATS. 

bling a seal. The onion, smilax, asparagus, lily of the valley, 
etc., are members of the lily family. The parts of the flower 
are usually in threes, though there is an exception in the genus 
Unifolium, where the parts are in twos. A remarkable excep- 
tion occurs sometimes in Trillium grandiflorum, where the flower 
is abnormal and the parts are in twos. 

492. Floral formula. — A formula is sometimes written to show at a glance 
the general points of agreement in the flower among the members of a 
family or group. The floral formula of the lily family is written as follows : 
Calyx 3, Corolla 3, Andrcecium 6(3-3), Gyncecium 3. The formula may be 
abbreviated thus: Ca3,Co3,A3,G3- 

493. Adheaon and cohesion. — In the lily family all the sets, or whorls of 
parts, are free ; that is, no floral set is adherent to another. Farther, the 
parts of the calyx, corolla, and andrcecium are distinct. But the parts of the 
gyncecium are coherent, i.e. the three carpels are united into a single com- 
pound pistil. In the floral formula this cohesion of the parts of a set is 
represented by a small bracket over the figure, as in the gyncecium of the 
lily family. 

494. Floral diagram. — The relation of the parts of the flower on the axis 
are often represented by a diagram, as shown in fig. 326 for the water- 
plantain family. 

495. Note. — In the following lessons on plant families practical exercises 
may be conducted, employing representative plants in the several important 

families. Sketches should be made of the form of the 
leaves, their relation to the stem ; stipules ; parts of 
the flower, and other salient and important characters. 
Floral formulas and diagrams may be made. Brief 
notes and descriptions, made from the specimens them- 
selves and not from the books, should be appended. 
The plants chosen here need not be insisted upon, for 
Fig. 326. others equally good may be found. The studies 

Diagram of alisma presented are offered as suggestions to indicate the 
flower. (Vines.) . . . , . . . . . . . 

way in which relationships may be detected, and a 

familiarity with the characters' of the families may be obtained. Several of 

these lessons are chosen among the monocotyledons, to which the lily family 

also belongs. 

496. Water-plantain family (alismaceae). — If we wish to begin with a 
more simple and primitive family, the water-plantain family will serve the 
purpose. The common water plantain (Alisma plantago) is an example. It 
occurs in ditches and muddy shores of streams and lakes. The flowers are 
in a loose panicle and are inconspicuous. The leaves resemble those of the 




PLANT FAMILIES: ORCHIDACE&. 



255 



plantain, hence the common name of water-plantain. The flower is regular 
(all parts of a set are alike), and all the parts are distinct and free. This 
represents a simpler and more primitive condition than exists in the lily 
family, where the carpels are united. The floral formula is as follows : 
Ca3,Co3,A6,G6 — oo ; i.e. the parts are in threesor multiples of three. The 
stamens are in pairs in front of the sepals, and really represent but three sta- 
mens, since it is believed each one has divided, thus making three pairs. No 
stamens stand in front of the petals in the water plantain, but in the 
European genus Bittomus one stamen in addition stands in front of each 
sepal. 

497. The arrow leaf (genus sagittaria) #occurs in wet ground, or on the 
margins of streams and ponds. The leaves are very variable, and this seems 
to depend to some extent on the depth of the water. Several forms of this 
plant are shown in figs. 493-495. The flowers are monoecious or dioecious. 

498. The orchid family (orchidaceae). — Among the orchids are found the 
most striking departures from the arrangement of the flower which we found 
in the simpler monocoty- 
ledons. An example of 
this is seen in the lady- 
slip per (cypripedium, 
shown in fig. 464). The 
ovary appears to be below 
the calyx and corolla. This 
is brought about by the 
adhesion of the lower part 
of the calyx to the wall 
of the ovary. The ovary 
then is inferior, while 
the calyx and corolla are 
epigynous. The stamens 
are united with the style 
by adhesion, two lateral 
perfect ones and one upper 
imperfect one. The stamens are thus gynandrous. The sepals and petals 
are each three in number. One of the petals, the ••slipper," is large, 
nearly horizontal, and forms the " lip" or ''labellum " of the orchid flower. 
The labellum is the platform or landing place for the insect in cross polli- 
nation (see Part III, Pollination). Above the labellum stands one of the 
sepals more showy than the others, the ''banner. " The two lateral 
••strings" of the slipper are the two other petals. The stamens are still 
more reduced in some other genera, while in several tropical orchids three 
normal stamens are present. 

499. There are thus four striking modifications of the orchid flower: 1st, 




Fig. 327. 
Flower of an orchid (epipactis), the inferior ovary 
twisted as in all orchids so as to bring the upper part of 
the flower below. 



• 5 r> 



MONOCOTYLEDONS. 



the flower is irregular (the parts of a let are different in size and shape); 2d, 
adnation od .ill parts with tin pistil; 3d, reduction and suppression of the 
stamens; 4th, the ovary istwisted hall waj around so that the posterior side 
of the flown- becomes anterior. Floral diagrams in fig. 328 show the posi- 




Fig. S a8. 

Diagrams of orchid flowers. '. tlu> usual 
typo; B t of cypripedium. (Vines.) 




Fig, s*> 
Diagram "t Bower 
of canua. 



tionofthe stamens in two distinct types. The number of orchid species is 
>vi \ large, and the majority are found in tropical countries. 

500. Related to the orchids are the iris family, in which the stigma is ex 
panded into the form of a petal, and the canna family. In the (.anna the 
flower is irregular (see figs, 4^7, 468) and the ovary is inferior, (See chap- 
ter on pollination. Tart III, for description of the canna llowor.) 



CHAPTER XXXVIII. 

MONOCOTYLEDONS CONCLUDED. 

Topic II : Monocotyledons with flowers on a spadix 
(Spadiciflorae). 

501. Lesson II. The arum family faraceaej. — This family 
is well represented by several plants. The skunk's cabbage 
( Spathyema fcetida) illustrated in figs. 455-457 is an interest- 
ing example. The flowers are closely crowded around a thick 
stem axis. Such an arrangement of flowers forms a "spadix" 
The spadix is partly enclosed in a large bract, the " spathe" 
The sepals and stamens are four in number, and the pistil has a 
four-angled style. The corolla is wanting. (See chapter on 
pollination, Part III, for farther characters of the flower. ) 

502. The " jack-in-the-pulpit," also called " Indian turnip " 
(Arisaema triphyllum), shown in f\g. 458, the water arum (Calla 
palustris), and the sweet flag (Acorns calamus; are members of 
this family, as also are the callas and caladiums grown in con- 
servatories. The parts of several of the species of this family, 
especially the conn of the Indian turnip, are very acrid to the 
taste. The floral parts are more or less reduced. 

503. Related to the arum family are the (i duckweeds. " 
Among the members of this family are the most diminutive of 
the flowering plants, as well as the most reduced floral structures. 

I For description and illustration of three of these duckweeds, 
hapter on nutrition in Part III.) 
Other related families are the cat-tails and palms. In the 
latter the spathe and spadix are of enormous size. The cocoa- 
nut is the fruit of the cocoanut palm. 

257 



258 



MONO CO T YLED OJVS. 



Topic III : Monocotyledons with a glume subtending 
the flower (Glumiflorae). 

504. Lesson III. Grass family (gramineae). Oat. — As a 

representative of the grass family (gramineae) one may take the 
oat plant, which is widely cultivated, and also can be grown 
readily in gardens, or perhaps in small quantities in greenhouses 
in order to have material in a fresh condition for study. Or w r e 
may have recourse to material preserved in alcohol for the dis- 




Fig. 334- 

„. „. „. Flower of 

Fig. 330. Fig. 331. Fig. 332. Fig. 333. oat> show . 

Spikelet of One glume re- Flower opened Section show- ingthe upper 

oat showing moved showing showing two palets, ing ground plan paletbehind, 

two glumes. fertile flower. three stamens, and of flower, a, axis, and the two 

two lodicules at base lodicules in 

of pistil. front. 

section of the flower. The plants grow usually in stools ; the 
stem is cylindrical, and marked by distinct nodes as in the corn 
plant. The leaves possess a sheath and blade. The flowers 
form a loose head of a type known as a panicle. Each little 
cluster as shown in fig. 330 is what is a spikelet, and consists 
usually here of one or two fertile flowers below and one or two 
undeveloped flowers above. We see that there are several 
series of overlapping scales. The two lower ones are "glumes," 



PLANT FAMILIES: GRAMINEjE. 



259 



and because they bear no flower in their axils are empty glumes. 
Within these empty glumes and a little higher on the axis of the 
spike is seen a boat-shaped body, formed of a scale, the margins 
of which are folded around the flowers within, and the edges 
inrolled in a peculiar manner when mature. From the back of 
this glume is borne usually an awn. If we carefully remove 
this scale, the "flower glume," we find that there is another 
scale on the opposite (inner) side, and much smaller. This is 
the "palet." 

505. Next above this we have the flower, and the most prom- 
inent part of the flower, as we see, is the short pistil with the two 
plume-like styles, and the three stamens at fig. 332. But if we 
are careful in the dissection 
of the parts we will see, on 
looking close below the pistil 
on the side of the flowering 
glume, that there are two 
minute scales (fig. 334). 
These are what are termed 
the lodicules, considered by 
some to be merely bracts, 
by others to represent a pe- 
rianth, that is two of the 
sepals, the third sepal hav- 
ing entirely aborted. Ru- 
diments of this third sepal Fi sr- 335- 

Diagram ot oat spikelet. CI, glumes ; B, palets; 

are present in some of the a, abortive flower. 
gramineae. 

506. To the gramineae belong also the wheat, barley, corn, 
the grasses, etc. The gramineae, while belonging to the class 
monocotyledons, are less closely allied to the other families of 
the class than these families are to each other. For this reason 
they are regarded as a very natural group. 




507. The sedge family (ey per aceae). Carex. — As a representative of the 
sedges a species of the genus carex may be studied. If plants of Carex 
lupulina are taken from the soil carefully we will find that there is an under- 



26o 



MONO CO T YLED ONS. 



ground stem or root-stock which each year grows a few inches, forms new 
attachments by roots to the soil, and thus the plant may spread from year 
to year. This underground stem, as seen, has only scaly leaves. The 
upright stems reach a height of two to three feet, and are prominently 

three-angled, as are most of 
the species of this large genus. 
The leaves are three-ranked, 
and consist of a long sheathing 
base and a long narrow blade. 
The flowers, as we see, are 
clustered at the end of the 
stem, or sometimes additional 
ones arise in the axils of the 
leaves lower down on the stem. 
The staminate flowers form a 
slender, short spike, terminat- 
ing the stem, while the pistil- 
late flowers form several 
spikes arising as branches. 





Fig. 336. 
Flowers of Carex lupulina ; staminate flower spike above, three 
pistillate flower spikes below. Details of pistillate and staminate 
Bowers shown at the right. 



The flowers are very much reduced here, and each of the pistillate flowers 
consists «»1 one pistil which i- surrounded by a flask-shaped scale, the/v;7- 
pynium. These perigynia can he distinctly seen upon the spike. At the 
.iprx «,i the perigynia the three styles emerge. Just below each perigynium 



PLANT FAMILIES: CYPERACEjE. 



26l 



is a blender scale, the primary bract, from the axil of which the pistillate 
flower arises. 




Fig. 337- 
Two carex flowers. 



Fig. 338. 
Pistil of carex. 



Fig. 339- 
Section of pistil. 



For the study of the flowers one must select material at the time the male 
flowers are in bloom. In fig. 340 is represented a portion of the staminate 
spike of Carex laxiflora. As 
seen here each staminate flower 
consists of three stamens. These 
stamens arise in the axil of a 
bract. Figure 337 represents 
a portion of the pistillate spike 
of the same species at the time 
of flowering. The fact that the 
parts, or members, of the flower 
are in threes suggests that there 
may be some relationship be- 
tween the carex and the monoco- 
tyledons already studied, even 
though each flower has become 
so reduced in the number of its 
members. 

508. In the bulrush (scirpus), 
another genus of this family, the 
flowers are perfect and complete 
(having all parts of the flower), 

with the parts in threes or some multiple of three, 
obvious resemblance to the monocotyledenous type. 




Fig. 340. 
Two male flov/ers of Carex laxiflora. 

Here there is a more 



CHAPTER XXXIX. 

DICOTYLEDONS. 

Topic IV: Dicotyledons with distinct petals, flowers 
in catkins, or aments ; often degenerate. 

509. Lesson IV. The willow family (salicacese).— The wil- 
lows represent a very interesting group of plants in which the 




Fig. 34 
Spray of willow leaves, pistillate and staminate catkins (Salix discolor). 

flowers are greatly reduced. The flowers are crowded on a 
more or less elongated axis forming a caiki?i, or ament. The 
anient is characteristic of several other families also. The 
willows are dioecious, the male and female catkins being borne 

262 



PLANT FAMILIES: CUPULIFERM. 



263 



on different plants. The catkins appear like great masses of 
either stamens or pistils. But if we dissect off several of the 
flowers from the axis, we find that there are many flowers, each 
one subtended by a small bract. In the male or " sterile " cat- 
kins the flower consists of two to eight stamens, while in the 
female or " fertile " catkins the flower consists of a single pistil. 
The poplars and willows make up the willow family. 

510. Lesson V. The oak family (cupuliferse). — A small 
branch of the red oak (Quercus rubral is illustrated in fig. 342. 




Fig. 342. 
Spray of oak leaves and flowers. Below at right is staminate flower, at left pistillate 



This is one of the rarer oaks, and is difficult for the beginner to 
distinguish from the scarlet oak. The white oak is perhaps in 



264 



DICOTYLEDONS. 



some localities a more convenient species to study. But for the 
general description here the red oaJ< will serve the purpose. Just 

j it t as the leaves are expand- 

ing in the spring, the deli- 
cate sprays 
of pendulous 
male catkins 
form beauti- 
ful objects. 
The petals 
are wanting 
in the flower, 
and the sepals 
form a united 

*ig- 343- 
Branch of the butter- 
nut. Cluster of female 
flowers at the top, show- 
ing the two styles of each 
pistil, catkins below. 

calyx, with several lobes, that is, the parts of the 

calyx are coherent. In the male flowers the calyx 

is bell-shaped and deeply lobed. The pendent 

stamens, variable in number, just reach below its 

margin. The pistillate or female flowers are not 

borne in catkins, but stand on short stalks, either singly or a few 

in a cluster. The calyx here is urn-shaped with short lobes. 

The ovary consists of three united (coherent) carpels, and there 

are three stigmas. Only one seed is developed in the ovary, 

and the fruit is an acorn. The numerous scales at the base of 

the ovary form a scaly involucre, the cup. 

511. The beech, chestnut, and oak are members of the oak 
family. 

512. The following additional families among the anient 
bearers are represented in this country : the birch family (birch, 
alder), the hazelnut family (hazelnut, hornbeam, etc.), walnut 
family (hickory, walnut), and the sweet-gale family (myrica). 





CHAPTER XL. 



DICOTYLEDONS CONTINUED. 

Topic V: Dicotyledons with distinct petals and 
hypogynous flowers. 

URTICIFLOR^E. 



513. The nettle family (urticaceae). — The nettle family receives its name 

from the members of one genus in which the stinging nettles are found 

(urtica). The dioecious nettle (U. dioica) has opposite, petioled leaves, 

which are ovate, with a heart-shaped base. The margins of the leaves are 




Fig. 344- 
The dioecious nettle (Urtica dioica), 
showing leaves, flower clusters, and 
below staminate flower at the right 
and pistillate flower at left. 




Fig. 345- 
Urtica, diagram of 
male flower. 




Fig. 346. 
Urtica, diagram of 
female flower. 



deeply serrate, and the lower surface is downy. The stems and petioles of 
the leaves are armed with stinging hairs. 

514. The greenish flowers are borne in dense clusters in the form of 
branched racemes which arise from the axils of the leaves. The staminate 

265 



266 



D ICO T YLED ONS. 



flowers have four small sepals and four stamens. The fertile flowers (pistil- 
late) have also four sepals. The pistil has a two-loculed ovary; one of the 
locules is the smaller, and later disappears, so that the fruit is a one-seeded 
achene. The parts of the flower are in twos, since the four sepals are in two 
pairs. 

515. Lesson VI. The elm family (ulmacege). — The elm tree 
belongs to this family. The leaves of our American elm (Ulmus 
americana) are ovate, pointed, deeply serrate, and with an ob- 
lique base as shown in fig. 347. The narrow stipules which are 




Fig- 347- 
Spray of leaves and flowers of the American elm ; at the left above is section of flower, 
next is winged seed (a samara). 

present when the leaves first come from the bud soon fall away. 
The flowers are in lateral clusters, which arise from the axils of 
the leaves, and appear in the spring before the leaves. They 
hang by long pedicels, and the petals are absent. The calyx is 
bell-shaped, and 4-9-clett on the margin. The stamens vary also 
in number in about the same proportion. A section of the 
flower in fig. 347 shows the arrangement of the parts, the ovary 
in the center. The ovary has cat her one or two locules, and two 
styles. The mature fruit lias one locule, and is margined with 
two winged expansions as shown in the figure. 'This kind of 
a seed is a samara. 



PLANT FAMILIES: PO 1 YG OX IFLORAL. 



267 



516. Buckwheat family (polj'gonacea?) 
from which this 
family gets i t s 
name, the k n ot - 
weeds arc good 
representatives. 
Fig. 348 is of the 
a now -leaved knot- 
weedj or arrow- 
leived tear-thumb, 
so called because 
of the arrow-shaped 
leaves and from the 
prominent recurved 
prickles on the four- 
angled stem. The 
plant occurs in low 
grounds often i n 
large clumps, and 
the slender branch- 
ed stem is support- 
ed to some extent by 
neighboring plants. 
The flowers are in 



POLYGONIFLOR^E. 

Besides the common buckwheat, 



Fig. 348. 

Polygonum sagittatum, portion 
of plant. 




Fig. 349- 
Spring beauty (Claytonia virginiana). 



268 DICOTYLEDONS, 

oval clusters borne on slender, long peduncles which arise from the axils of 
the leaves. Petals are wanting, and the calyx is usually five-parted, with 
the margin colored. The stamens are mostly eight, and the styles three on 
the compound ovary. There is a single seed developed in the ovary which 
in ripening forms a three-angled achene like a buckwheat grain. The 
species of dock, and of field, or sheep, sorrel (rumex) also belong to this 
family. 

CURVEMBITrVE. 

517. The purslane family (portulacaceae). — The little spring beauty (Clay- 
tonia virginica), shown in fig. 349, is a member of this family. It occurs 
in moist places. The stem arises from a deeply buried tuber, and bears, 
about midway, two long, narrow, fleshy, thick leaves. The upper part of 
the stem bears a raceme of pretty rose -colored flowers. The sepals are two. 
The petals are five in number, and the stamens of the same number are 
inserted on little claws at the base of the petals. The ovary has a long 
style, three-cleft at the apex, and in fruit it forms a three-valved pod. The 
ovule in claytonia and other members of the family is curved, and conse- 
quently the embryo is curved. 

518. In some other related families, like the goosefoot family, the embryo 





Fig. 350- 
Curved embryos of Russian thistle (Salsola soda). (Warming.) 

is also curved. In fig. 350 is shown the embryo of the Russian thistle 
(Salsola kali), a member of this family. 



POLYCARPICy€. 

519. Lesson VII. The crowfoot family (ranunculaceae). — 

The marsh-marigold (Caltha palustris) is a member of this family. 
The leaves are heart-shaped or kidney-shaped, and the edge is 
crenate. The bright golden -yellow flowers have a single whorl 
of petal-like envelopes, and according to custom in such cases 
they are called sepals. The number is not definite, varying from 



PLANT FAMILIES: RANUNCULACEM. 



269 



five to nine usually. The stamens are more numerous, as is the 

general rule in the members of 
the family, but the number of 
the pistils is small. Each one is 
separate, and forms a little pod 
when the seed is ripe. The marsh - 
marigold, as its 
name implies, oc- 
curs in marshy or 
wet places and 
along the muddy 
banks of streams. 
It is one of the 
common flowers in April and 
May. 

520. Many of the crowfoots 
or buttercups (ranunculus) with 
bright yellow flowers grow in 
similar situations. The "wood 
anemone" (anemone), small 

Fig. 352 plants with white flowers, and the rue- 

Diagram of marsh mangold r 

flower, anemone (anemonella), which resembles 

it, both flower in woods in early spring. The common virgin's 
bower (Clematis virginiana) occurs along streams or on hill- 
sides, climbing over shrubs or fences. 
The vine is somewhat woody. The 
leaves are opposite, petioled, and are 
composed of three leaflets, which are 
ovate, three-lobed, and usually 
strongly toothed, and somewhat 
heart-shaped at the base. The 
flower clusters are borne in the axils 
of the leaves, and therefore may also 
be opposite. The clusters are much 
branched, forming a convex mass of 
beautiful whitish flowers. The sepals are colored and the petals 





Fig. 353- 
Diagram of aquilegia flower. (Vines ) 



2 JO 



DICOTYLEDONS. 



may be absent, or are very small. The stamens are numerous, 

as in the members of the crowfoot family. 

The pistils are also numerous, and the 

achenes in fruit are tipped with the long 

plumose style, which aids them in floating 

in the air. 





Fig. 354- 
Clematis virginiana ; below at right are pis- 
tillate and staminate flowers. 



Fig- 355- 
Isopyrum biternatum. 



521. Some of the characters of the ranunculaceae we recognize 
to be the following : The plants are mostly herbs, the petals are 
separate, and when the corolla is absent the sepals are colored 
like a corolla. The stamens are numerous, and the pistils are 
cither numerous or few, but they are always separate from each 
other, that is they arc not fused into a single pistil ( though some- 
times there is but one pistil). All the parts of the flower are 
separate from each other, and make Up successive whorls, the 
pistils terminating the scries. When the seeds are ripe the fruit 
is formed, and may be in the form of a pod, or achene, or in the 
form of a berry, as in the bancberry (actaea |. 



PLANT FAMILIES: RANUNCULACEJE. 



271 



522. The following families arc related to the crowfoot family. The water- 
lily family, the magnolia family, and the barberry family with the May-apple 
as an example (see figure r/^ 

300). In all there is a 
relationship shown by the 
separate and usually 
numerous carpels. To- 
gether they form a large 
group, the polycarpica?. 




523. The poppy family (papaveraceae). 
— One of the commonest of the members 
of this family in the eastern United States 
s the bloodroot (Sanguinaria canadensis). 
It occurs in open woods in April and May. 
It derives its name from the abundant red 
juice (latex) in the perennial root-stock. 
The low annual shoot bears usually a 
single white flower, and one leaf, some- 
Details ot times more. The floral formula is as fol- 
lows: Ca2,Co8(or 10), A 00 .G2. 
524. The fumitory family (fumariaceae). — To this family belong the singu- 
lar plants, " dutchinan's breeches " and " squirrel-corn " (dicentra). They 
occur in rich woods in April and May. In the squirrel-corn (I), canaden- 
sis) there is a slender underground stem which bears here and there, as shown 



Bloodroot (sanguinaria). 
flower at left. 



272 



DICOTYLEDONS. 



in fig. 357) small yellow tubers resembling grains of corn. The leaves are 
compound, and the lobes are finely dissected. The flower scape bears a 
slender raceme of curious pendulous, greenish-white flowers, sometimes tinged 
with rose color. The details are shown in the figure. The stamens are six 
in number, arranged in two groups of three (being in two groups they are 
diadelphoiis). 

525. Lesson VIII. The mustard family (cruciferae). — This 
is well represented by the toothwort 
(dentaria), which we studied in a former 
chapter. 

These three families (poppy, fumitory, 
and mustard) are closely related as shown 
by the regular flowers, which are usually in 
twos (dimerous) or in fours (tetramerous). 





Fig. 358. 

Diagram of cruciferous 
flower. 



GRUINALES. 

527. Lesson IX. The gera- 
nium family (geraniaceae). 
— The wild cranesbill has a 
perennial underground root- 
stock. From this in the 
spring arises the branched, 
hairy stem. The leaves are 
deeply parted into about five wedge-shaped lobes, which are 
again cut. The peduncles bear several purple flowers (fig. 359). 
The floral formula is as follows : Ca5,Co5,Aio,G5« The wood- 
sorrel (oxalis), the balsam or jewelweed (impatiens), sometimes 
called " touch-me-not," are members of the same family. 



P 



Fig. 359- 
Branch of cranesbill (Geranium maculatum) 
showing upper leaves, flowers, and pods. 



CHAPTER XLI. 

DICOTYLEDONS CONTINUED. 



Topic VI : Dicotyledons with distinct petals and 

perigynous or epigynous flowers. 

Many trees and shrubs. 



^€SCULIN^. 



528. Lesson X. The maple family (aceracese). — Figure 360 
represents a spray of the leaves and flowers of the sugar maple 




Fig. 360^. 
Spray of leaves and flowers of the sugar maple. 

(Acer saccharinum), a large and handsome tree. The leaves are 
opposite, somewhat ovate and heart-shaped, with three to five 

273 



274 



DICOTYLEDONS. 



lobes, which are again notched. The clusters of flowers are pen- 
dulous on long hairy pedicels. The petals are wanting. The 






Fig. 360^. 
Seeds and flowers of sugar maple. At the right 1 
a pistillate flower, in the middle a staminate flower 
and at the left the two seeds torming a samara. 

calyx is bell-shaped and several times 
lobed, usually five times. The sta- 
mens are variable in number. The 
ovary is two-lobed and the 
deeply forked. The fruit forms 
two seeds, each with a long 
wing-like expansion as shown 
in the figure. The flowers of 
the maple are polygamo-dice- 
cious, that is the male members (sta- 
mens) and female members (carpels) 
may be in the same flower or in dif- 
ferent flowers. 

SAXIFRAGIN^E. 

529. The saxifrage family (sax- 
ifragaceae). — The early saxifrage 
(Saxifraga virginiensis) is a small 
plant \o-2^cm high, and grows on 
rocky and dry hillsides (fig. 361). 

The Ovate Or heait-shaped leaves Early saxifrage (Saxifraga virginiensis). 

have crenate margins, and are clustered near the ground. The 
scape bears a branched cluster of flowers at the summit. Floral 
formula Ca5,Co5,Aio,G2. 



PLANT FAMILIES : ROSIFLORA*:. 



?75 



ROSIFLOR>E. 



530. Lesson XI. — The rose-like flowers are an interesting and 
important group. In all the members the receptacle (the end of 
the stem which bears the parts of the flower) is an important part 
of the flower. It is most often widened, and either cup-shaped or 
urn-shaped, or the center is elevated. The carpels are borne in the 
center in the depression, or on the elevated central part where 
the receptacle takes on this form. The calyx, corolla, and the 
stamens are usually borne on the margin of the widened recep- 
tacle, and where this is on the margin of a cup-shaped or urn- 
shaped receptacle they 
are said to heperigynous, 
that is, around the gyn- 
cecium. The calyx and 
corolla are usually in 
fives. There are three 
families, as follows. 

531. The rose fam- 
ily (rosaceae). — In this 
family there are five 
types, represented by the following plants and illustrations: 
1st. In spiraea (fig. 362) the receptacle is cup-shaped. There 

are five carpels, united at the 
base, but free at the ends. 
2d. In the strawberry the re- 
ceptacle is conic and bears the 
carpels (f\g. 363). The conic 
receptacle becomes the fleshy 
fruit, with the seeds in little pits 
over the surface. 3d. The rasp- 
berries, blackberries, etc., represented here by the flowering 
raspberry (Rubus odoratus), fig. 364. 4th. This is represented 
by the roses. The receptacle is urn-shaped and constricted 




Fig. 362. 
Perigynous flower of spiraea (S. lanceolata). 
Warming.) 



(From 




Fig. 363- 

Flower of Fragaria vesca with columnar 

receptacle I From Warming.) 



276 



DICOl^YLEDONS. 




toward the upper portion, 
with the carpels enclosed 
in the base (fig. 365). 
5 th. Here the receptacle is 
cup-shaped or bell-shaped 
and nearly closed at the 
mouth as in the agrimony. 



Fig. 364. 
Flowering raspberry (Rubus odoratus). 



Fig. 365- 
Perigynous flower of rosa, with 
contracted receptacle. (From 
Warming.) 



532. Lesson XII. The almond or plum family (amygdala- 
ceae). — The members of this family are trees or shrubs. The 
common choke-cherry (fig. 366) will serve to represent one of 
the types. The flowers of this species are borne in racemes. 
The receptacle is cup-shaped. Only one seed in the single 
carpel (sometimes two carpels) matures as the calyx falls away. 
The outer portions of the ovary become the fleshy fruit, while 
the inner portion becomes the hard stone with the seed in the 
center. Such a fruit is a drupe. 

The floral formula for this family is as follows: 

Ca5,Co5,Ai5-2o or 30, Gi. 

533. Lesson XIII. The apple family (pomaceae). — This fam- 
ily is represented by the apples, pears, quinces, june-berries, haw- 
thorns, etc. The members are trees or shrubs. The receptacle is 
somewhat cup-shaped and hollow. The perianth and stamens 



PLANT FAMILIES: POMACES. 2J7 

are at first perigynous, but become epigynous (upon the gynce- 
cium) by the fusion of the receptacle with the carpels. The floral 




Fig. 366. 
Choke-cherry (Prunus virginiana). Leaves, 
flower raceme, and section of flower at right. 

formula is thus Ca5,Co5, A 10-5-5 or IO - IO- 5>Gi-5. The carpels 




Fig. 367. 
Flower of pear. (After Warming.) 



are united, but the styles are free. In fruit the united carpels fuse 
more or less with the receptacle. 



278 



DICOTYLEDONS. 



LEGUMINOS^E. 



534. Lesson XIV. The pea family (papilionaceae). — This 

family is well represented by the common pea. The flower is 




Fig. 368. 
Details of pea flower ; section of flower, perianth removed to show the diadelphous 
stamens, one single one, and nine in the other group. (From Warming.) 

butterfly-like ox papilionaceous, and the showy part is made up of 
the five petals. The petals have received distinct names here 
because of the position and form in the 
flower. At fig. 369 the petals are separated 
and shown in their corresponding posi- 
tions, and the names are there given. The 
flower is irregular aud the parts are in fives, 
except the carpel, which is single. The 
calyx is gamosepalous (coherent), the 
corolla polypetalous (distinct). The ten 
stamens are in two groups, one separate 
stamen and nine united ; they are thus 
diadelphous (two brotherhoods). The 
fruit forms a pod or legume, 
maturity splits along both edges. 

535. There are three families in the legume-bearing plants : 
1st, including the locusts, cassias, etc.; 2d, the pea family, in- 
< hiding peas, beans, closers, ground-nuts, or peanuts, vetches, 
desmodiuni, etc.; 3d, including the sensitive plants like mimosa. 




Fig. 369. 
Corolla of pea. S, stand- 
ard ; //', wines; A", two 
and at petals forming lceel. 



PLANT FAMILIES: ONOGRACEM. 



279 




Fig. 370. 
Evening primrose (CEnothera biennis) showing flower buds, flowers, and seed pods. 
(From Kemer and Oliver. 1 



28o 



DICOTYLEDONS. 



Topic VII: Dicotyledons with distinct petals and 
epigynous flowers. 



MYRTIFLORy£. 

536. Lesson XV. The evening -primrose family (onogra- 
ceae). — In the evening primrose (Oenothera) the flowers are ar- 
ranged in a loose spike along 
the end of the stem, each one 
situated in the axil of a leaf- 
like bract. The flowers of the 
family are very characteristic, as 
shown here. They are sessile 
in the axil of the bract, and the 
calyx forms a long tube by the 
union of the sepals, only the end 
of the tube being divided into 
the individual parts, showing 
four lobes. On the edge of the 
open end of the calyx tube are 
seated the four, somewhat heart- 
shaped, yellowish petals, and 
here are also seated the eight 
stamens. The four carpels are 
united into a single pistil within 
the base of the calyx tube and 
united with it, so that the calyx 
tube seems to be on the end of 
the pistil. The flowers soon 
fade and fall away from the pistil, 
and this grows into an elongated 
four-angled pod. Since the 
lower flowers on the stem are the older, we find nearly mature 
fruit and fresh flowers, with all intermediate grades, on the 
same plant. 

The plants grow by roadsides and in old fields. They are from 
\ocrn to a meter or more high (one to five feet). The leaves are 




Section 



flower 



PLANT FAMILIES: ONOGKACE^E. 



28l 



lanceolate or oblong, toothed and repand on the margin. In 
many of the species of the family the parts of the flower are in 
fours as in the evening primrose, but in others the number is 
variable. 




Fig. 372. 
Wild carrot. 

UMBELLIFLOR^E. 



537. The parsley family (umbelliferae). — The wild carot (Daucus carota) is 
common by roadsides and in old fields during August and September. The 
leaves are deeply divided and the lobes are notched (pinnately decompound). 
The flowers form umbels, since the pedicels are all of about the same length, 
and many of them radiate from the same point. In the carrot, and in most of 



282 



DICOTYLEDONS. 



the parsley family, the umbel is a compound one, as shown in the illustration. 
The calyx is firmly united with the walls of the ovary, which is formed of two 
united carpels. The live white petals as well as the five stamens arise from the 




Fig- 373- 

Single umbel of the wild carrot. 



margin of the ovary around the two styles. No portion of the calyx is free in 
the wild carrot, though in some other members of the family there are small 




Fig. 376. 
Seed "i \\ ilil 1 arrot 



< .il\ \ iccili. The frail < s bristl) and the surface of the umbel becomes con- 
cave in ag< . I lie Bora! formula is as follows: Ca5,Co5,A5,G2, 

I he cornel or dogwood famil) and the aralia family both have the flowers 
in umbels, and are thus related to the parsley family. 



CHAPTER XUI. 



DICOTYLEDONS CONCLUDED. 
SYMPETAL/E. 

538. In the remaining families the corolla is gamopetalous, 
that is, the petals are coherent into a more or less well -formed 
tube, though they may be free at the end. For this reason they 
are known as the sympetalce. 

Topic VIII: Dicotyledons with united petals, flower 
parts in five whorls. 

BICORNES. 

539. The pyrola family (pyrolaceae). — The shin-leaf or wintergreen (Py- 
rola elliptica), not the aromatic wintergreen, 
is figured at 377. The oval or elliptical leaves 
are clustered at the base. The flower scape 
is 15-30 cm high and bears a raceme at the 
summit. The flowers hang singly from the 
axils of colorless bracts. The floral formula 
is as follows : Ca5,Co5. Aio,G5. The Indian- 
pipe (monotropa) is also a member of the pyrola 
family. 



540. Lesson XVI. The whortle- 
berry family (vacciniacese). — The 

common whortleberry, or huckleberry 
(Gaylussacia resinosa), flowers in May 
and June. The shrubs are from 300?/ 
to 1 meter (1-3 feet) high, and are 
much branched. The leaves are ovate, 
and when young are more or less 
clammy from numerous resinous dots, 
from which the plant gets its specific 
name (resinosa). The flowers are borne on separate shoots from 

283 




Fig- 377- 
Pyroia elliptica. 



284 



DICO T YLED ONS. 




the leaves of the same season, and hang in one-sided short ra- 
cemes as shown in fig. 378. The calyx is short, five-lobed, 

and adheres to the ovary. The corolla 
is tubular, at length cylindrical with 
five short lobes, and is whitish in color. 
The stamens are ten in 
number, and the com- 
pound ovary has a sin- 
gle style. The fruit is 
a rounded black, edi- 
ble berry or drupe, 

.., , -, Fi S- 379- 

With ten Seeds. Diagram of Erica. 

(Vines.) 
541. The family ericaceae 

contains the trailing arbutus, cassandra, andro- 

meda, cassiope, etc. The rhododendron family 

contains the rhododendrons, azaleas, kalmias, 

etc. These with the pyrola and whortleberry 

families are closely related and make up the order heaths, or Bicornes as they 

are sometimes termed, because the anther frequently 

has two horn-like appendages. 

PRIMULIN>E. 

542. The primrose family (primulaceae). — The 

primroses (primula) represent well this family. In fig. 

453 is represented the flower of the primrose grown 

in conservatories. It is gamosepalous and gamopeta- 

lous. There are five stamens, each one inserted on flower. (Vines.) 

the tube of the corolla and opposite the lobe. (For a description of the flower 

see chapter on pollination, Part III.) The floral formula is Ca5,Co5,A5,G5. 




Fig. 378. 
Whortleberry (Gaylussacia re 
sinosa). 




Fig. 380. 
Diagram of primula 



Topic IX: Dicotyledons with united petals, flower 
parts in four whorls. 



TUBIFLOR^. 



543. The morning glory or bindweed family (convolvulaceee). — The 
hedge bindweed (Convolvulvus sepiumj occurs in moist soil along streams. 
The stem is twining as in most of the members of the family. The leaves are 



PLANT FAMILIES: PERSONATE. 



>8 5 




Fig 
Morning-glory (Convol- 
vulus sepium). 



arrow- or halberd-shaped, and the gamopetal- 
ous corolla is white or rose color. The corolla 
forms a broad funnel-shaped tube, and is 
twisted or convolute in the 
bud, as in all the mem- 
bers of the family. Floral 
formula : Ca5,Co5,A5,G2. 
The five sepals are covered 
by two large bracts. Other 
members of this family are 
the morning-glory, sweet potato, 
cypress vine, the parasitic dodder, 
etc. 

PERSONATE. 

544. The nightshade family 
(solanacese). — Fig. 382 represents 
the ground- cherry (physalis), a mem- 
ber of this family. The formula 
for the flower is Ca5,Co5,A5,G2. 
The calyx becomes enlarged and 
inflated, enclosing the edible berry. 
The potato, egg-plant, tomato, to- 



bacco, etc., are members of the 
nightshade family. 

545. The figwort family (scro- 
phulariaceae). — The mullein (ver- 
bascum), toad-flax (linaria), turtle- 
head (chelone), etc , are members of 
the figwort family. The plants are 
mostly herbs. The stamens are 
usually didynamous (four in two 
pairs, one pair shorter than the 
other) or diandrous (tw r o stamens). 
The stamens are inserted on the 
two lipped corolla tube, which is 
more or less irregular. In some 
genera there are five stamens, as in 
verbascum. 

546. The borage family (boragi- 
nacese). — The pretty little forget- 




Fig. 382. 
Ground-cherry (Physalis pennsylvanica). 



2S6 



DICOTYLEDONS. 



me-not belongs to this family. The flowers are borne in a curved and more or 

less one-sided (helicoid) cyme as shown in fig. 383. 
The plant grows in wet low ground. The flower 
stalks are forked, and continue to grow and 
blossom all through the summer. The corolla 
is rotate (wheel-shaped), the spreading blue 
lobes with a yellow scale on each at the throat of 
the tube. Alternating with these scales are the 
five short stamens. The ovary is four-divided, 
and in fruit forms four nutlets. 




Fig. 383. 
Forget-me-not. 



NUCULIFER^E. 




Fig. 384. 
Spray of dead-nettle (Lamium am- 
plexicaule), leaves and flowers. 



547. Lesson XVII. The mint 
family (labiatse). — The mint 
family contains a large number 
of genera and takes its common 
name from the mints, of which 
there are several species belong- 
ing to the genus mentha. In the figure of the ki dead-nettle " 
(Lamium amplexicaule), which is also one of the members of 
this family, we see that the lobes of the irregular corolla are 
arranged in such a manner as to suggest two lips, an upper and 
a lower one. From this character of the corolla, which obtains 
in nearly all the members, the family receives its name of 
Labiates. The calyx is five-lobed. The stamens, four in number, 
arise from the tube of the corolla, and converge in pairs. The 
ovary is divided into four lobes, and at the maturity of the seed 



PLANT FAMILIES: LABI ATM. 



287 



these form four nutlets. The leaves are rounded, crenate on the 
margins, the lower ones petioled and heart- 
shaped, and the upper ones sessile and clasp- 
ing around the stem beneath the flower clusters. 
From the clasping character of the upper leaves 
the plant derives its specific name of ampleoci- 
cau/e. The plant occurs in waste places and is 
rather common. ^. ^s* 385 ; 

Diagram of laimum 
flower. 




CONTOR'TVE. 



548. The gentian family (gentianaceae). — The gentians usually appear 
late in the summer or autumn. The fringed gentian (fig. 386) lingers often 




Fig. 386. 
Gentian (G. crinita). 



Fig. 387. 
The bluet (Houstonia ccerulea). 



288 



DICOTYLEDONS. 



until the snow arrives. The flower is gamosepalous and gamopetalous. 
The corolla is bell-shaped, with four lobes. The lobes are blue in color, 
somewhat spreading, and beautifully fringed on the margin. The members 
of the gentian family have opposite, simple leaves, and no stipules. The 
ovary has a single cavity, but is formed of two united carpels as shown by 
the two stigmas, and usually two placentae. 



RUBIALES. 

549. Lesson XVIII. The honeysuckle family (caprifoli- 
acese). — The members of this family are mostly shrubs (a few 
herbs) with opposite leaves. Flowers are gamosepalous and 
gamopetalous. The ovary is 2-5 -celled, and coherent with the 




Fig. 388. 
Partridge-berry (Mitchella repens). 



Fig. 389. 
Wild honeysuckle (Lonicera ciliata). 



„~ A 



tube of the calyx. The corolla is tubular, or wheel-shaped, and 
the stamens are inserted on its tube. The fly -honeysuckle (Loni- 
cera ciliata), shown in fig. 389, is an example, with a tubular or 
funnel-shaped, nearly regular corolla. The corolla has a small 
spur at the base, and the flowers are in pairs. 

550. The twin flower (LinnseS borealis) occurs in cold situa- 



PLAA r 7' FAMILIES: DIPSACACEJE. 



289 




Fig. 390. 
Twin flower (Linnaea borealis). 



tions in moors or damp woods, and blossoms in June. The 
stems are creeping and slender, 
the leaves rounded and crenate 
on the margin, tapering abrupt- 
ly into short petioles. From the 
prostrate stems the flowering 
shoots arise 8-1 oc??i, leafy be- 
low, and above forking into two 
slender pedicels, each bearing a 
bell-shaped, purple and whitish 
flower. The calyx is coherent 
with the ovary, which has three 
locules. The five lobes of the 
calyx fall away as the flower 
dies. The corolla is five-lobed. 
Four stamens, two of them shorter than the other two, are at- 
tached to the -tube of the corolla. 

551. Lesson XIX. The teasel family (dipsacacese). — This 
family is represented by the common fuller's teasel. The flowers 
are collected in a u head." They are separated from one an- 
other, however, by a small cup-shaped i ' epicalyx ' ' which sur- 
rounds the inferior ovary. The limb of the calyx is short, and 
in some members of the family shows the five divisions. In the 
teasel there are four lobes on the limb of the corolla, which is 
unsymmetric and bilabiate (zygomorphic), two of the five parts 
of the corolla being completely united into one lobe, forming the 
upper lip. The stamens are not united by their anthers. (The 
distinct stamens and the presence of the epicalyx separating the 
flowers of the head are the most prominent characters separating 
the dipsacales from the aggregate. ) 



CAMPANULINyE. 



552. The bell-flower family (campanulaceae). — The bell-flower (cam- 
panula) is illustrated in figure 458. The floral formula is as follows : 
Ca5,Co5,A5,G2. The stamens are usually united by their anthers closely 
around the style. The style is provided with a brush of hairs, and m 



290 



DICOTYLEDONS. 



pushing its way up between the anthers brushes off some of the pollen and 
bears it aloft, where it becomes attached to visiting insects. 

The lobelia family is related to the bell-flower family, and contains the 
cardinal-flower, great lobelia, and others. 



AGGREGATE. 



553. 



Lesson XX. The composite family (compositse). — In 

all the composites, the flowers 
are grouped (aggregated) into 
" heads," as in the sunflower, 
where each head is made up of 
a great many flowers crowded 
closely together on a widened 
receptacle. The family is a 
large one, and is divided into 
several sections according to 
the kinds of flo"wers and the 
different ways in which they 
are combined in the head. In 
the asters there is one common 
type illustrated in fig. 391 by 
the Aster novce-anglice. In the 
aster, as is well shown in the 
figures, the head is composed 
of two kinds of flowers, the 





Fig. 391. 
Aster nti\ .1 angliae. 



Fig. 392. 
ad of flowers of Aster nova-anglias. 



PLANT FAMILIES : COMPOSITE. 



29I 



tubular flowers and the ray flowers. In the tubular flowers 
the corolla is united to form a slender tube, which is five-notched 
at the end, representing the five petals. In the ray flowers the 
corolla is extended on one side into a strap-shaped expansion. 
Together these strap-shaped corollas form the "rays" of the 
head. The corolla is split down on one side, which permits 
the end then to expand and form the "strap." This is a 




Fig. 393- 
Ray flower of Aster novae " 
angliae. 



Fig. 394- Fig. 395. Fig. 396. 

Tubular flower Tubular flower Syngenecious 
of aster. opened to show syn- stamens opened to 

genecious stamens. show style and two 

stigmas. 



ligula y or more correctly speaking a false ligula. In fact the ray 
flower is bilabiate. By counting the "teeth" of the false ligula 
there are found only three, which indicates that the strap here 
is made up of only three parts of the 5-merous corolla. The 
two other limbs of the corolla are rudimentary, or suppressed, 
on the opposite side of the tube. True ligulate flowers are 
found in the chicory, dandelion, or in the hieracium, where the 
five points are present on the end of the ligula. 

554. The calyx tube in the aster, as in all of the composites, 
is united with the ovary, while the limb is free. In the aster, as 
in many others, the limb is divided into slender bristles, the 
pappus. (In some of the composites the pappus is in the form 01 



292 



DICOTYLEDONS. 




scales. ) The stamens are united by their anthers into a tube 
(syngenecious) which closely surrounds the style. (In am- 
brosia the anthers are sometimes distinct. ) The style in pushing 
through brushes out some of the pollen from the anthers and 
bears it aloft as in the bell-flower, but the stigmatic surface is 
not yet mature and expanded, so that close pollination cannot 
take place. There are usually no stamens in the ray-flowers. 
The ovary is composed of two carpels, as is 
shown by the two styles, but there is only one 
locule, containing an erect, anatropous, ovule. 

The floral formula for the composite family \ 
then is as follows: Ca5, C05, A5, G2. 

555. The rattlesnake- weed (Hieracium veno- 
sum) is an example of another type, with only _ Flg ' 3 ? 7 ' 

/ r ;1 ' J Diagram of composite 

one kind of flower in the head, the true ligu- flowei: - ( vines ) 

late flower. The hawkweed, or devil's 
paint-brush (H. aurantiacum) is a re- 
lated species, which is a troublesome 
weed. The dandelion and prickly 
lettuce are also members of the ligulate- 
flowered composites. A number of 
the composites have only tubular 
flowers, as in the thoroughwort (eu- 
patorium) and everlasting (anten- 
naria). 

556. The extent to which the union of the 
parts of the flower has been carried in the 
composites, and the close aggregation of the 
flowers in a head, represent the highest stage 
of evolution reached by the flowers of the 
angiosperms. The composites stand just 
above the bell-flowers and lobelias, at the 
termination of a series. The teasels show 
a relationship to the composites in the aggre- 
gation of the flowers in a head. But the con- 
solidation of the parts of the flower has not been carried so far, and the 
flower- arc eacb separated l>v an "epicalyx " in the form of a minute cup- 
shaped involucre. The teasels stand .it the termination of another series in 




Fig. 398. 

Rattlesnake-weed (Hieracium ve 
no sum). 



PLANT FAMILIES: COMPOSITE, 293 

which are the lonicera and valerian families. The gyncecium of the com- 
posites presents a highly specialized structure. The ovary is plainly made 
up of two carpels, as shown by the two styles and the internal structure, 
but it becomes reduced to a one-seeded achene. From the five carpels in 
the pyrolas to the composites there is a gradual tendency toward reduction 
in number of the carpels to two, and in the composites the highest speciali- 
zation is reached in the consolidation of these into one achene in fruit. 



CHAPTER XLIII. 

OUTLINE OF TWENTY LESSONS IN THE 
ANGIOSPERMS. 

557. As a minimum study of the plant families in the angio- 
sperms, the following twenty lessons are suggested to represent 
nine topics. 

MONOCOTYLEDONS. 

Topic I : Monocotyledons with conspicuous petals. 

Lesson I : Liliaceae, lily family. 
Topic II : Monocotyledons with flowers on a spadix. 

Lesson 2 : Araceae, arum family. 
Topic III : Monocotyledons with a glume subtending the 
flower. 

Lesson j: Gramineae, grass family. 

DICOTYLEDONS. 

Topic IV: Dicotyledons with distinct petals, flowers in catkins 
or aments, often degenerate. 
Lesson 4: Salicacese, willow family. 
Lesson 5 : Cupuliferae, oak family. 
Topic V: Dicotyledons with distinct petals, and hypogynous 
flowers, not in true catkins. 
Lesson 6: Ulmacese, elm family. 
Lesson 7 .• Ranunculaceae, crowfoot family. 

294 



OUTLINE OF TWENTY LESSONS. 295 

Lesson 8 : Cruciferae, mustard family. 
Lesson 9: Geraniaceae, geranium family. 
Topic VI : Dicotyledons with distinct petals, and perigynous 
or epigynous flowers. Many trees and shrubs. 
Lesson 10: Aceraceae, maple family. 
Lesson 11 : Rosaceae, rose family. 
Lesson 12 : Amygdalaceae, almond family. 
Lesson ij: Pomaceae, apple family. 
Lesson 14: Papilionaceae, pulse family. 
Topic VII : Dicotyledons with distinct petals and epigynous 
flowers. 
Lesson ij: Onograceae, evening primrose family ; or Um- 
belli ferae, parsley family. 
Topic VIII : Dicotyledons with united petals, flower parts in 
five whorls. 
Lesson 16 : Vaccineaceae, whortleberry family. 
Topic IX : Dicotyledons with united petals, flower parts in 
four whorls. 
Lesson 17 : Labiatae, mint family. 
Lesson 18 : Caprifoliaceae, honeysuckle family. 
Lesson 19: Dipsacaceae, teasel family. 
Lesson 20: Compositae, composite family. 

558. Synopsis of families studied in the angiosperms. — 

The following synopsis of the families of the angiosperms is in- 
tended for reference in grouping the studies in order that the 
relationships of the families may be graphically represented. 
The tables therefore should not be memorized. 

559. Table of families of monocotyledons studied. — In the 
monocotyledons there is a single cotyledon on the embryo ; the 
leaves are parallel-veined ; the parts of the flower are generally 
in threes, and endosperm is usually present in the seed. There 
are a few exceptions to all these characters. Thus a single 
character is not sufficient to show relationship in groups, but one 
must use the sum of several important characters. 

The families of monocotyledons can be grouped into three 
large divisions as follows : 



296 ANGIOSPERMS. 

MONOCOTYLEDONS. 

Petaloide^ : Conspicuous petals (or perianth) are the charac 
teristic feature. 

Alismacece ; water-plaintain family, alisma, etc. 

Liliacece ; lily family, trillium, lily, etc. 

CannacecB ; canna family. 

Orchidacece ; orchid family. 
Spadiciflor^e : The spadix and spathe are characteristic. 

Aracece ; arum family, skunk's cabbage, jack-in-the-pulpit, etc. 

LemnacecB ; duckweed family, lemna, wolffia, etc. 

Pahnacece ; palm family. 
Glumiflorae : The subtending bract (glume) at the base of 
the flower is characteristic. 

Graminece ; grass family. 

Cyperacece ; sedge family. 

560. Table of families of dicotyledons studied (a few other 
families are introduced in the scheme). In the dicotyledons 
there are two cotyledons on the embryo \ the venation of 
the leaves is reticulate; the endosperm is usually absent, and 
the parts of the flower are frequently in fives. There are 
exceptions to all the above characters, and the sum of the 
characters must be considered, just as in the monocotyledons. 

DICOTYLEDONS. 

I. Chori petals ; the petals are distinct. 

*. Amentiferce, ament- or catkin-bearing plants. 
Saliciflor^e : Both kinds of flowers in catkins. 

Salicacece ; willow family, poplars and willows. 
Querciflor/e : Pistillate flowers in acorns or cones. 

Betulacece ; birch family, birch, alder, etc. 

Corylacece ; hazelnut family, hazelnut, hornbeam, etc. 

Cupuliferce ; oak family, oak, chestnut, beech. 
Juglandiflor^; : Pistillate flowers form nuts in fruit. 

Juglandacew ; walnut family. 

**, Choripetalce proper, flower not degenerate. 



OUTLINE OF TWENTY LESSONS. 297 

I. Flowers hypo gy nous. 

Urticiflor^ : Flowers not in true aments. 

Urticacecs ; nettle family. 

UlmacecB ; elm family. 
Polygoniflor.^e : Fruit a triangular or lenticular achene. 

Polygonacece ; knotweed family, knotweed, buckwheat. 
Curvembry^e : Embryo curved in the seed. 

Poriulacacece ; pursley family, claytonia (spring beauty). 

Caryophyllacece ; pink family, carnation, corn-cockle, etc. 

Chenopodiacece ; pigweed family, pigweed, beet, Russian 
thistle, etc. 
Polycarpic^e : Carpels usually numerous and always distinct. 

RanuncuIacecB ; buttercup family (crowfoot family), butter- 
cups, marsh-marigold, clematis, etc. 

Nympheacece ; water-lily family. 

Berberidacece ; barberry family, mandrake, etc. 
Rhceadin.e : The flowers are dimerous or tetramerous. 

PapaveracecB ; poppy family, bloodroot, etc. 

Fumariacea ; fumitory family, squirrel-corn, dutchman's- 
breeches. 

Crucifercz ; mustard family, toothwort, cabbage, turnip, etc. 

Droseracece ; sundew family, sundew, venus -flytrap, etc. 

Violacece ; violet family. 

Sarraceniacece ; pitcher-plant family. 
Gruinales : Carpels united, styles prolonged into a beak. 

Oxalidacece ; oxalis family. 

Linacece ; flax family. 

Geraniacece ; geranium family, cranesbill, etc. 
Columnifer^e : Stamens usually united by their filaments into 
a column. 

Malvacece ; mallow family, hollyhock, cotton, etc. 

2. Flowers per igy nous or epigynous. 

^sculin^e : Stamens arising from a glandular disk, trees or 

shrubs. 



298 A NGIOSPERMS. 

Sapindaceaz ; soap-berry family, horse-chestnut, etc. 
Aceracece ; maple family. 
Frangulinve : Includes the holly family, vine family, etc. 
Saxifragin^: Flower generally perfect and regular, stamens 
5 or 10, carpels few (2-5). 
Saxifragacece ; saxifrage family; also currant, witch-hazel, 
and sycamore families. 
Rosiflor^e : Flowers regular, stamens and carpels usually 
numerous, trees and shrubs mostly. 
Rosacea ; rose family, strawberry, blackberry, rose, etc. 
Amygdalacece ; almond family, peach, apricot, plum, cherry, 

etc. 
Pomacece ; apple family, apple, quince, pear, hawthorn, june- 
berry, etc. 
Leguminos^e : Flower papilionaceous, carpel single, forming a 
pod or legume. 
Papilionacece ; pulse family, pea, bean, vetch, etc. 
Mimosacece ; mimosa family, sensitive plants. 

j. Flowers epigynou 

Passiflorin^e : Fruit of three carpels, but with one locale and 
three parietal placentae. Here belong the passion-flower, 
begonia, and cucurbit families. 
Myrtiflor/E: Calyx usually prolonged beyond the inferior 
ovary, flowers usually 4-merous. 
OnagracecE ; evening-primrose family. 
UMBELLiFLORiE : Mowers in umbels, sepals and petals small. 
Cornaceaz ; dogwood family. 
UmbeUiferw ; parsley family. 



II. Symi-i; 1 \i„! . Petals coherent (gamopetalous). 






1. Flowers pentacy die 1 that is, parts in five whorls (stamens in 

two whorls). 
BlCORNES : Mostly shrubs, flowers usually 4-5-merous, stamens 
frequently with two-horned anthers. 



OUTLINE OF TWENTY LESSONS. 299 

Pyrolacece ; pyrola family, pyrola, [ndian-pipe, etc. 
Ericacece ; heath family. (Also rhododendron and whortle- 
berry families.) 
PRiMULiNiE : One-celled ovary, seeds on a central column, 
corolla salver -form. 
Primulacece : primrose family. 

2. Flowers tetracyclic, that is, the parts in four whorls. 
TubifloRj*:: Gamopetalous corolla not split, the five parts in- 
dicated by a slight unevenness of the margin, corolla twisted 
in bud. 
Convolvulacece ; bindweed family, morning-glory, dodder, 
etc. 
Personaive: Flowers frequently bilabiate (the nightshade 

family represents this group). 
NucuLiFERiE : Calyx gamosepalous ; gamopetalous corolla usu- 
ally bilabiate, carpels usually two, forming four nutlets. 
Boraginacece ; borage family, forget-me-not, etc. 
Labia tee ; mint family, dead-nettle, catnip, etc. 
Contortve : The corolla is twisted in the bud, but is split into 
five lobes. 
Gentianacece ; gentian family. 
Rubiales : Leaves opposite with stipules, or veiticillate. 
Rubiacece, ; madder family, bluet. 
Caprifoliacece ; honeysuckle family, lonicera, etc. 
Dipsacales : Flowers in a head (in one family), no stipules, 
anthers distinct. 
Valerianacece ; valerian family. 
Dipsacacecc ; teasel family. 
Campanulin^e : Flowers not in heads, anthers united. 

Campanidacece ; bellflower family. 
Composite : Flowers in heads, anthers united. 

Composi/<r ; composite family, aster, solidago, sunflower, 
dandelion, etc. 



ECOLOGY. 
INTRODUCTION. 

561. While we are engaged with the study of the life pro- 
cesses concerned in nutrition and growth of plants, with the 
details of form, structure, and systematic relationship, we should 
not overlook the mutual relationships which exist among plants 
in their natural habitat, and the phenomena of growth recurring 
with the seasons, and influenced by environment, or due to 
inherent qualities. By a study of the life histories of plants, 
their habits and behavior under different conditions of environ- 
ment, we shall broaden our concept of nature and cultivate our 
aesthetic, observational, and reasoning faculties. The subject is 
too large for full treatment within the limits of a part of an 
elementary book. The way here can only be pointed out, and 
the few examples and illustrations, it is hoped, will serve to open 
the book of nature to the young student, and lead him to study 
some of the problems which are presented by every region. 
This study of plants, in their mutual and environmental relation- 
ships, is ecology. 

562. For beginning classes, where only a small part of the 
time is available, excursions can be made from time to time dur- 
ing the year for this purpose, taking certain subjects for each ex- 
cursion. For example, in the autumn one may study means for 
the dissemination of seeds, protection of seeds, plant formations, 
zonal distribution of plants, formation of early spring flowers, 
etc. ; in the winter, twigs and buds, protection of plants against 
the cold ; and in the spring, opening of the buds and flowers, 
pollenation, etc., and farther studies on plant societies, relation 
of plants to soil, topography, etc 

300 



ECOLOGY. 3 01 

563. In carrying on studies of this kind one should bear in 
mind the factors which influence plants in these relationships, 
that is, what are called the ecologic factoj-s ; in other words, 
those agencies which make up the environmental conditions of 
plants, all of which play a greater or lesser role in the habit or 
status of the plant concerned, and which, acting on all plants 
concerned, give the peculiar color or physiognomy to the plants 
of a region or of a more restricted community. 

Such factors are climate, with its modifying meteorological 
conditions ; texture, chemistry, moisture content, covering, to- 
pography, exposure, etc. , of the soil ; influence of light and 
heat ; of animals, of plants themselves, and so on. 



CHAPTER XLIV. 

WINTER BUDS, SHOOTS, ETC. 

564. Winter buds and how the young leaves are protected. — In plants 
like the pea, bean, corn, etc., which we have been studying, when the plant 
is mature it ripens its seed, and then dies. It grows only for one season, 
and the plants of the next , season are obtained from the seed again. Such 
plants are annual. In woody plants like trees and shrubs which grow from 
year to year, the young growing ends, where the elongation of the shoot or 
branch will take place the coming year, are usually provided with a special 
armature for protection during the cold of the winter, or through the resting 
pericd. This growing end is the bud. One of the very common means of 
protection of the buds through the rigor of the winter is by means of bud 
scales, which are formed at the close of the season's growth, and which 
overlap and closely hide the young and tender bud leaves within. Atten- 
tion is called to a few of these buds here, and there will be no difficulty for 
the student to obtain quantities of material of several different kinds of trees 
and shrubs which it may be desirable to study, and which need not be men- 
tioned here. 

565. Twigs and buds of the horse-chestnut. — In fig. 399 is illustrated a 
shoot of the horse-chestnut. At the end of the shoot there is a large termi- 
nal bud, and at its base are two lateral buds. The terminal bud is broader 
than the diameter of the shoot, and is ovate in form. We notice that there 
are a number of scales which overlap each other somewhat as shingles do on 
a roof, only they are turned in the opposite direction. If we begin at the 
base of the bud, we can see that the two lowest scales are opposite each 
other, and that the two next higher ones are also opposite each other, and 
set at right angles to the position of the lower pair. In the same manner 
successive pairs of scales alternate, so that the third, fifth, seventh, etc., are 
exactly over the first, and the fourth, sixth, etc.. are exactly over the second. 
Aside from the fact that these brown scales fit closely together over the bud, 
we notice that they are covered with a sticky substance which helps to keep 
out the surface water. Thus a very complete armature i< provided for the 
protection of the young leaves inside. 

566. Leaf scars. The number of leaves developed during one season's 

302 






WINTER BUDS, SHOOTS, ETC. 



I! 



' M 



growth in length of the shoot can be determined by count- 
ing the broad whitish scars which arc situated just below 
each pair of lateral buds. Near the margin of these sens 
in the horse-chestnut are seen prominent pits arranged in 
a row. These little pits in the leaf scar are formed by 
the breaking away of the fibrovascular bundles (which 
run into the petiole of the leal) as the leaf falls in the 
autumn. 

567. Lateral buds. — The lateral buds, it is noticed, 
arise in the axils of the leaves. Each one of these by 
growth the next year, unless they remain dormant, will 
develop a shoot or branch. Just above the junction of the 
upper pair of branches we notice scars which run around 
the shoot in the form of slender rings, several quite close 
together. These are the scars of the bud scales of the 
previous year. By observing the location of these ring 
scars on the stem, the age of the branch may be deter- 
mined, as well as the growth in length each year. Small 
buds may be frequently seen arising in the axils of the bud 
scales, that is after the scales have fallen, so that four to 
ten small buds may be counted sometimes on these very 
narrow zones of the shoot. 

568. Bud leaves. — On removing the brown scales of the 
bud there is seen a pair of thin membranous scales which 
are nearly colorless. Underneath these are young leaves ; 
successive pairs lie farther in the bud, in outline similar to 
the mature leaves, and each pair smaller than the one just 
below it. They are very hairy, with long white woolly 
fibres. These woolly fibres serve also to protect the young 
leaves from the cold or from sudden changes in the tem- 
perature, since they hold the air in their meshes very 
securely. 

569. Opening of the buds in the spiing. — As the buds 
"swell" in the spring of the year, when the growth of 
the young leaves and of the shoot begins, the bud scales 
are thrown backward and soon iall away as the leaves 
unfold, thus leaving the ••ring scar" which marks the 
start of the new year's growth in length of the shoot. 

570. A study of a number of different kinds of woody 

shoots would serve to show us a series of very interesting . 

variations in the color, surface markings, outline of the showing buds and kit 

scars. (A twig with 
branch, arrangement oi the leaves and consequently dif- a terminal bud should 

ferent modes of branching, variations in the leaf scars, the u^rfi^re.) 6160 ^ ^ 



Fig. 399- 

Two year-old twig 



304 



ECOLOGY. 



form, size, color, and armature of the buds, as well as great variations in 
the character of the bud scales. There are striking differences between the 
buds of different genera, and with careful study differences can also be seen 
in the members of a genus. 

571. Growth in thickness of woody stems. — In the growth of woody per- 
ennial shoots, the shoot increases in length each year at the end. The 

shoot also increases in diameter each 
year, though portions of the shoot one 
year or more old do not increase in 
length. We can find where this 
growth in diameter of the stem takes 
place by making a thin cross section 
of a young shoot or branch of one of 
the woody plants. If we take the 
white ash, for example, in a cross 
section of a one-year-old shoot we 
observe the following zones : A cen- 
tral one of whitish tissue the cells of 
which have thin walls. This makes 
a cylindrical column of tissue through 
the shoot which we call the pith or 
medulla. Just outside of this pith 
is a ring of firmer tissue. The inner 
portion of this ring shows many 
woody vessels or ducts, and the outer 
portion smaller ducts, and a great 
many thick-walled woody cells or 
fibres. This then is a woody zone, 
or the zone of xylem. 

572. The outer ring is made up of 
the bark, as we call it. In this part 
are the bast cells. Between the bark 
and the woody zone is a ring of small 
Fig. 400. cells with thin and delicate walls, and 

Three-year-old twig of the American ash, with the cel j s are r i c her in protoplasm, 
sections of each year s growth showing annual * x 

rings. If the section is stained, these cells 

are apt to show a deeper color than either the wood zone or the bast zone. 
This is, as we will recollect from our study of the bundle in stems, the cam- 
bium zone, or the growing part of the older portions of the stem. 

573. We may wish to know why these portions of the bundle here form a 
continuous or apparently a continuous ring in the stem of a woody plant. In 
the study of the sunflower stem, and also of impatiens, attention was called 
to the increase in the number of the bundles as the stem increased in age. 




WINTER BUDS, SHOOTS, ETC. 30$ 

If we happened to examine quite old portions of these stems, we would have 
observed that a large part or the entire portion of the thin-walled tissue, sep- 
arating the woody portions of adjacent bundles, had changed to thick-walled 
or woody tissue, so that there is here in the older portions of the sunflower 
plant a continuous ring of xylem. This is the case also to some extent with 
the bast tissue. We already have noticed that the cambium ring in these 
stems is a continuous one, although the cambium between the bundles of the 
sunflower plant was not so active as that in the bundle proper. There is, 
however, a difference between the tissue lying between adjacent bundles and 
that of the bundle itself. 

574. The bundles in the ash stem and in other woody stems lie very 
closely side by side, so that at first it might appear as if they were continu- 
ous. We note, however, that there are radiating lines which extend from the 
pith out toward the bast. These run between the bundles. These radiat- 
ing lines are formed by the tissue lying between the bundles becoming 
squeezed into thin plates, which extend up and down between the bundles. 
They are termed the medullary rays,* since they radiate from the pith or 
medulla. These are shown well in a section of an oak stem. 

575. Difference in the firmness of the woody ring. — We have already 
noted that the inner portion of the wood zone contains more and larger ducts 
than the outer zone, and that in the outer portion of the same zone the woody 
fibres predominate. The ducts are formed during the early spring growth, 
and later in the season the development of the fibres predominates. 

576. Annual rings in woody stems. — If we now cut across a shoot of the 
ash which is several years old, we will note, as shown in fig. 400, that there 
are successive rings which have a similar appearance to the woody ring in 
the one-year-old stem. This can well be seen without any magnification. 
The larger size of the woody ducts which are developed each spring, and 
the preponderance of the fibres at the close of each season's growth, mark 
well the growth in diameter which takes place each year. 

577. While the thickened walls of all the cells give strength to the wood, 
the different kinds of cells vary in the percentage of strength which they 
give. Thus the bast cells which have very thick walls are yet more flexible 
than the wood fibres, as can be seen if one strips off some of the bark of the 
basswood tree. Again, the woody fibres give more strength to wood than 
the same diameter of wood vessels, because they are much more firmly 
bound together, and the ends are long and tapering, and are spliced over 
each other where cells below and above meet. In the case of the wood 
vessels the ends do not taper out so much, or in some cases they meet ad- 
jacent cells below or above squarely. 

578. Wood then which has a large number of wood vessels compared with 
the fibres, or in which the size of the vessels is great, is not so strong as 

* Rays, or radiating plates, of tissue appear also in the bundle. 



306 ECOLOG V. 

wood which has a large percentage of fibrous elements, and in which the 
ducts are comparatively small. Wood with numerous large vessels is also 
more spongy, and therefore lighter than woods with a close fibrous struc- 
ture. We should find it an exceedingly interesting study if we made a 
comparative examination of the growth and strength of the different woods. 

579. Phyllotaxy, or arrangement of leaves. — In our study of the organs 
which utilize carbon for food, and in examining buds on the winter shoots of 
woody plants, we could not fail to be impressed with some peculiarities in the 
arrangement of these members on the stem of the plant. Even in the liver- 
worts and mosses we note that where there is any indication of leaf-like 
expansions on a central axis there is a general plan of arrangement of these 
leaf-like structures over successive zones of the axis. 

In the horse-chestnut, as we have already observed, the leaves are in pairs, 
each one of the pair standing opposite its partner, while the pair just below or 
above stand across the stem at right angles to the position of the former pair. 
In other cases (the common bed straw) the leaves are in whorls, that is several 
stand at the same level on the axis, distributed around the stem. By far the 
larger number of plants have their leaves arranged alternately. A simple ex- 
ample of alternate leaves is presented by the elm (fig. 347), where the leaves 
stand successively on alternate sides of the stem, so that the distance from one 
leaf to the next, as one would measure around the stem, is exactly one half 
the distance around the stem. This arrangement is 1/2, or the angle of diver- 
gence of one leaf from the next is 1/2. In the case of the sedges the angle of 
divergence is less, that is 1/3. 

By far the larger number of those plants which have the alternate arrangement 
have the leaves set at an angle of divergence represented by the fraction 2/5. 

580. Other angles of divergence have been discovered, and much stress has 
been laid on what is termed a law in the growth of the stem with reference to 
the position which the leaves occupy. There are, however, numerous excep- 
tions to this regular arrangement, which have caused some to question the 
importance of any theory like that of the ' * spiral theory ' ' of growth propounded 
by Goethe and others of his time. 

581. As a result, however, of one arrangement or another we see a beauti- 
ful adaptation of the plant parts to environment, or the influence which envi- 
ronment, especially light, has had on the arrangement of the leaves and 
branches of the plant. Access to light and air are of the greatest importance 
to green plants, and one cannot fail to be profoundly impressed with the work- 
ings of the natural laws in obedience to which the great variety of plants have 
worked out this adaptation in manifold ways. 



CHAPTER XLV. 



SEEDLINGS. 



582. An interesting period in the life of plants is during germination, when 
the embryo plant comes out of the seed and lifts its leaves and stem above the 
ground. Tn the germinating corn plant the young leaves are wrapped around 
one another and enclose the stem, form- 
ing a long, slender, pointed sheath, if it 
may be so called. As this pushes its way 
through the soil it stands erect, with the 
pointed end uppermost. Because of its 
form and the compactness with which the 
leaves are wrapped together, it easily 
wedges its way through the soil, with no 
harm to the tender leaves and stem. 

583. The pea seedling comes out of 
the ground in a very different way. By 
the swelling of the two thick cotyledons 
the outer coat of the seed is cast partly 
off, the root emerges on one side, and the 
short stem is curved between 
the cotyledons in the form of 
an arch. The cotyledons re- 
main in the soil, while the 
arched stem, as it elongates, 
pushes its way 
through the soil. 
The leaves 





Fig. 401. 
How the garden bean comes out of the ground. First the looped hypocotyl, then the 
cotyledons pulled out, next casting off the seed coat, last the plant erect, bearing thick 
cotyledons, the expanding leaves, and the plumule between them. 

307 



3o8 



ECOLOG V. 



the pea are broader and shorter than the leaves of the corn, and cannot well 
form a long pointed covering for the stem. If the stem remained straight 
the friction of the leaves against the soil would tear them while they are so 
tender. But lifted out as they are, suspended from the bent stem, they are 
unharmed. 

584. The common garden bean. — The bean also in swelling cracks open 
the outer coat, the root emerges from underneath the coat in the region of the 
scar (hilum) on the concave side, while the minute plumule lies curved between 
the edges of the cotyledons near one end. In the case of the bean, the part 
of the stem between the cotyledons and the root (called the hypocotyl in all 
seedlings) elongates, so that the cotyledons are lifted from the soil. The hypo- 
cotyl is the part of the stem here which becomes strongly curved, and the large 
cotyledons are dragged out of the soil as shown in fig. 401. The outer coat 
becomes loosened, and at last slips off com- 
pletely. The plumule (the young part of the 
stem with the leaves) is now pushing out from 
between the cotyledons. As the cotyledons 
are coming out of the ground the first pair of 
leaves rapidly enlarge, so that before the stem 
has straightened up there is a considerable leaf 
surface for the purpose of car- 
bon conversion. The leaves 
are at first clasped together, 
but as the stem becomes erect 





Fig. 402. 
Germination of castor-oil bean. 



they are gradually parted and come to stand out nearly in a horizontal posi- 
tion. Fig. 401 shows the different positions, and we see that the same pro- 
vision for the protection of the leaves is afforded as in the case of the pea. 
As the cotyledons become exposed to the light they assume a green color. 
Some of the stored food in them goes to nourish the embryo during germina- 
tion, and they therefore become smaller, shrivel somewhat, and at last fall off. 
585. The castor-oil bean. — This is not a true bean since it belongs to a 
very different family of plants (euphorbiace<-e). In the germination of this 
seed a very interesting comparison can be made with that of the garden bean. 
As the " bean'' swells the very hard outer coat generally breaks open at the 



SEEDLINGS. 



309 



free end and slips off at the stem end. The next coat within, which is also 
hard and shining black, splits open at the opposite end, that is at the stem 
end. It usually splits open in the form of three ribs. Next within the inner 
coat is a very thin, whitish film (the remains of the nucellus, and correspond- 
ing to the perisperm) which shrivels up and loosens from the white mass, the 
endosperm, within. In the castor-oil bean, then, the endosperm is not all 
absorbed by the embryo during the formation of the seed. As the plant 
becomes older we should note that the fleshy endosperm becomes thinner and 
thinner, and at last there is nothing but a thin whitish film covering the green 
faces of the cotyledons. The endosperm has been gradually absorbed by the 
germinating plant through its cotyledons and used for food. 

586. How the embryo gets out of a pumpkin seed. — We should not fail 
to germinate some seeds of a pumpkin or squash. Some of the seeds should 






Fig. 403. 

Seedlings of castor-oil bean casting the seed coats, and showing papery remnant of the 
endosperm. 



be sown in the soil, and some on damp sphagnum covered with moist paper, 
or between the folds of a damp cloth, first soaking them for ten to twelve 



3TO 



ECOLOG Y. 



hours. The pumpkin seed is the one we have selected for this study. It 
will be instructive first to examine those which have been germinated in the 




Fig. 404. 

Germinating seed of pumpkin, showing how the heel or " peg " catches on the seed coat 
to cast it off. 

folds of moist cloth and paper, so that they can readily be observed at all 
stages, without digging them up from the soil. 

587. The root pushes its 
way out from between the 
stout seed coats at the 
smaller end, and then turns 
downward unless prevented 
from so doing by a hard 
surface. After the root is 
2-\cm long, and the two 
lalves of the seed coats 
have begun to be pried 
apart, if we look in this rift 
at the junction of the root 
and stem, 
we will 
s e e that 
one end 
of the seed coat is caught 
against a heel, or "peg," 
which lias grown out from 
the stem for this purpose. 
Now if we examine one 
which is a little more ad- 
vanced, we will see this 
heel more distinctly, and 
also that the stem < hypo 
cotyl) is arching out away 
from the seed coats, As 




I > ape of the pumpkin seedling from the seed coats. 



SEEDLINGS. 



3" 



the stem arches up its back in this way it pries with the cotyledons against 
the upper seed coat, but the lower seed coat is caught against this heel, and 
the two are pulled gradually apart. In this way 
the embryo plant pulls itself out from between 
the seed coats. In the case of seed which are 
planted deeply in the soil we do not see this con- 
trivance unless we dig down into the earth. The 
stem of the seedling arches through the soil, pull- 
ing the cotyledons up at one end. Then it 
straightens up, the green cotyledons part, and 
open out their inner faces to the sunlight, as 
shown in fig. 406. If we dig into the soil we 
will see that this 
same heel is formed 
on the stem, and 
that the seed coats 
are cast oft" into the 
soil. 

Fig. 406. 
Pumpkin seedling rising from the ground. 





Arisaema triphyllum. 

588. Germination of seeds of jack-in-the-pulpit. — The ovaries of jack-in- 
the-pulpit form large, bright red berries with a soft pulp enclosing one to 




Fig. 407. 
Seedlings of jack-in-the-pul- 
pit ; embryo backing out of the 
seed. 





Fig. 408. 
Section of germinating embryos of 
jack-in-the-pulpit, showing young 
leaves inside the petiole of the coty- 
ledon. At the lett cotyledon shown 
surrounded by the endosperm in the 
seed ; at right endosperm removed to 
show the club-shaped cotyledon. 



several large seeds. The seeds are oval in form. Their germination is inter- 
esting, and illustrates one type of germination of seeds common among 



312 



ecolog y. 



monocotyledonous plants. If the seed are covered with sand, and kept in a 
moist place, they will germinate readily. 

589. How the embryo backs out of the seed. — The embryo lies within the 
mass of the endosperm ; the root end, near the smaller end of the seed. The 
club-shaped cotyledon lies near the middle of the seed, surrounded firmly on 
all sides by the endosperm. The stalk, or 
petiole, of the cotyledon, like the lower 
part of the petiole of the leaves, is a hollow 
cylinder, and contains the younger leaves, 
and the growing end of the stem or bud. 
When germination begins, the stalk, or 
petiole, of the cotyledon elongates. This 
pushes the root end of the embryo out at 
the small end of the 
seed. The free end 
of the embryo now 
enlarges somewhat, 




Fig. 409. 
Seedlings of jack-in-the- 
pulpit, first leaf arcliing out 
of the petiole of the coty 
ledon. 




Fig. 410. 

Embryos of jack-in-the-pulpit still 
attached to the endosperm in seed 
coats, and showing the simple first 
leaf. 



Fig. 411. 

Seedling of jack-in- 
the-pulpit; section of 
the endosperm and 
cotyledon. 



as seen in the figures, and becomes the bulb, or corm, of the baby jack. At 
first no roots are visible, but in a short time one, two, or more roots appear on 
the enlarged end. 



SEEDLINGS. 313 

590. If we make a longisection of the embryo and seed at this time we can 
see how the club-shaped cotyledon is closely surrounded by the endosperm. 
Through the cotyledon, then, the nourishment from the endosperm is readily 
passed over to the growing embryo. In the hollow part of the petiole near 
the bulb can be seen the first leaf. 

591. How the first leaf appears. — As the embryo backs out of the seed, 
it turns downward into the soil, unless the seed is so lying that it pushes 
straight downward. On the upper side of the arch thus formed, in the 
petiole of the cotyledon, a slit appears, and through this opening the first leaf 
arches its way out. The loop of the petiole comes out first, and the leaf later, 
as shown in fig. 409. The petiole now gradually straightens up, and as it 
elongates the leaf expands. 

592. The first leaf of the jack-in-the-pulpit is a simple one. — The first leaf 
of the embryo jack-in-the-pulpit is very different in form from the leaves which 
we are accustomed to see on mature plants. If we did not know that it 
came from the seed of this plant we would not recognize it. It is simple, 
that is it consists of one lamina or blade, and not of three leaflets as in the 
compound leaf of the mature plant. The simple leaf is ovate and with a 
broad heart-shaped base. The jack-in-the-pulpit, then, as trillium, and some 
other monocotyledonous plants which have compound leaves on the mature 
plants, have simple leaves during embryonic development. The ancestral 
monocotyledons are supposed to have had simple leaves. Thus there is in 
the embryonic development of the jack-in-the-pulpit, and others with com- 
pound leaves, a sort of recapitulation of the evolutionary history of the leaf in 
these forms. 



CHAPTER XLVI. 



FURTHER STUDIES ON NUTRITION. 

593. In our former studies on nutrition we found that such 
plants as the corn, pea, bean, etc., obtain their liquid food 
through the medium of root hairs. The liverworts and mosses 
obtain theirs largely through similar outgrowths, the rhizoids, 
while a majority of the algae, being bathed on all sides by water, 
absorb liquid food through any part of the surface. We will find 
it instructive to study some of the different ways in which diverse 
plants obtain their liquid food. 

594. Nutrition in lemna. — A water plant is illustrated in fig. 412. This 
is the common duckweed, Lemna trisulca. It is very peculiar in form and in 




Fronds ot the duckweed (Lemna trisulca 



its mode of growth. Each one of the lateral leaf-like expansions extends out- 
wards by the elongation of the basal part, which becomes long and slender. 
Next, two new lateral expansions are formed on these by prolification from near 



NUTRITION: WOLFFIA. 



315 



the base, and thus the plant continues to extend. The plant occurs in ponds 
and ditches and is sometimes very common and abundant. It floats on the 
surface of the water. While the flattened part of the plant resembles a leaf 
it is really the stem, no leaves being present. This expanded green body is 
usually termed a •• frond." A single rootlet grows out from the under side 
and is destitute of root hairs. Absorption of nutriment therefore takes place 
through this rootlet and 
through the under side 
of the •' frond." 

595. Spirodela polyr- 
rhiza. — This is a very 
curious plant, closely re- 
lated to the lemna and 
sometimes placed in the 
same genus. It occurs 
in similar situations, and 

is very readily grown in aquaria. It reminds 
one of a little insect as seen in fig. 413. There 
a iv >everal rootlets on the under side of the 
frond. Absorption of nutriment takes place 
here in the same way as in lemna. 

596. Nutrition in wolffia. — Perhaps the most curious of these modified 
water plants is the little wolfna, which contains the smallest specimens of the 




Fig- 413- 
Spirodela polyrrhiza 




Fig. 414- Fig. 415. . Fig. 416. 

Young frond of wolffia Young frond of wolffia Another species o f 
growing out of older one. separating from older one. wolffia, the two fronds 

still connected. 

flowering plant-. Two species of this genus are shown in figs. 414-416. 
The plant body is reduced to nothing but a rounded or oval green body, which 



3i6 



ECO LOG Y. 



represents the stem. NO Leaves <>r roots are present. The plants multiply 
by " prolification," the new fronds growing out from a depression on the under 
side ot one end. 

597. Nutrition of lichens. -Lichens are very curious plants which grow 
on rocks, on the trunks and branches of trees, and on the soil. They form 
leaf-like expansions more or less green in color, or brownish, or gray, or they 
occur in the form of threads, or small tree-like formations. Sometimes the 
plant fits so closely to the rock on which it grows that it seems merely to 
paint the rock a slightly different color, and in the case of many which occur on 
trees there appears to be to the eve only a very slight discoloration of the bark 
of the trunk, with here and there the darker colored points where fruit bodies 




Fig 417. 
Frond of lichen (peltigera), showing rhizoids. 

are formed. The most curious thing about them is, however, that while they 
form plant bodies of various form, these bodies are of a ''dual nature" as 
regards the organisms composing them. The plant bodies, in other words, are 
formed of two different organisms which, woven together, exist apparently 
a- one. A fungus on the one hand grows around and encloses in the 
meshes of its mycelium the cells or threads of an alga, as the case may l>e. 

If we take <>ne of tin- leaf-like forms known as peltigera, which grows on 
damp soil or on the surfaces () f badly decayed Logs, we see that the plant 
body i^ flattened, thin, crumpled, and irregularly lobed. The color is dull 
greenish on the upper side, while the under side is white or light gray, and 
mottled with brown, especially the older portions. Here and there on the 

under surfaee are quite long slender blackish strands. These are composed 

entirely of fungus threads and serve as organs of attachment or holdfasts, 

and for the purpose of supplying the plant body with mineral substances 



NUTRITION: LICHENS. 



317 



which are in solution in the water of the soil. If we make a thin section of 
the leaf-like portion of a lichen as shown in fig. 418, we shall see that it is 
composed of a mesh of colorless threads which in certain definite portions 
contain entangled green cells. The colorless threads are those of the fungus, 
while the green cells are those of the alga. These green cells of the alga per- 
form the function of chlorophyll bodies for the dual organism, while the threads 
of the fungus provide the mineral constituents of plant food. The alga, 
while it is not killed in the embrace of the fungus, does not reach the per- 




Fig. 418. 
Lichen (peltigera), section of thallus ; dark zone of rounded bodies made up largely of the 
algal cells. Fungus cells above, and threads beneath and among the algal cells. 

feet state of development which it attains when not in connection with the 
fungus. On the other hand the fungus profits more than the alga by this 
association. It forms fruit bodies, and perfects spores in the special fruit 
bodies, which are so very distinct in the case of so many of the species of 
the lichens. These plants have lived for so long a time in this close associa- 
tion that the fungi are rare'y found separate from the algae in nature, but in 
a number of cases they have been induced to grow in artificial cultures sep- 
arate from the alga. This fact, and also the fact that the algae are often 
found to occur separate from the fungus in nature, is regarded by many as an 
indication that the plant body of the lichens is composed of two distinct or- 
ganisms, and that the fungus is parasitic on the alga. 



US 



ECOLOG )'. 



598. Other- regard the Lichens .is autonomous plants, thai is, the two or- 
ganisms have by this long-continued community of existence become unified 
into an individualized organism, which possesses a habit and mode of life 








#i^^ 




r : ..c 4x9, 
Section ol fruit body or apothecium of lichen (parmelia), showing asci and spores of the 
fungus. 

distinct from that of either of the organisms forming the component parts. 
This community of existence between two different organisms is called by 
some vtutuaiism, or 1 



Nitrogen gatherers. 
599. How clovers, peas, and other legumes gather nitrogen. It has long 
been known that clover plants, peas, beans, and 
many other Leguminous plants arc often able to 
thrive in soil where the cereals do but poorly. 
Soil poor in nitrogenous plant food becomes richer 
in this substance where clovers, peas. etc.. are 
grown, ami the} are often planted tor the purpose 
o( enriching the soil. Leguminous plants, espe- 
^ ciallv in poor soil, are almost certain to have en- 
largements, in the form of nodules, or •• root 
tubercles." A root k^[ the common vetch with 
some ot these root tubercles is shown in fig, 420. 

600. A fungal or bacterial organism in these 
root tubercles. If we cut one ot these root tuber- 
cles open, and mount a small portion o[ the in- 
terior in water tor examination with the micro- 
SCOpe, we will find -mall nut-shaped bodies, 




K>>ot of the 1 ommon vet< 1 
showing root lube i 



. 



NUTRITION: NITROGEN GATHERERS. 



319 



some of which resemble bacteria, while others arc more or less forked into 
forms like the letter Y, as shown in fig. 421. These bodies are rich in 
nitrogenous substances, or proteids. They are portions of a minute organism, 
of a fungus or bacterial nature, which attacks the roots of leguminous plants 





Fig. 421. Fig. 422. 

Root-tubercle organism from vetch, old con- Root-tubercle organism from Medicago 
dition. denticulata. 

and causes these nodular outgrowths. The organism (Phytomyxa legumi- 
nosarum) exists in the soil and is widely distributed where legumes grow. 

601. How the organism gets into the roots of the legumes. — This minute 
organism in the soil makes its way through the wall of a root hair near the 
end. It then grows down the interior of the root hair in the form of a 
thread. When it reaches the cell walls it makes a minute perforation, 
through which it grows to enter the adjacent cell, when it enlarges again. 
In this way it passes from the root hair to the cells of the root and down to 
near the center of the root. As soon as it begins to enter the cells of the 
root it stimulates the cells of that portion to greater activity. So the root 
here develops a large lateral nodule, or "root tubercle." As this "root 
tubercle" increases in size, the fungus threads branch in all directions, 
entering many cells. The threads are very irregular in form, and from cer- 
tain enlargements it appears that the rod -like bodies are formed, or the 
thread later breaks into myriads of these small "bacteroids." 

602. The root organism assimilates free nitrogen for its host. — This 
organism assimilates the free nitrogen from the air in the soil, to make the 
proteid substance which is found stored in the bacteroids in large quantities. 
Some of the bacteroids, rich in proteids, are dissolved, and the proteid sub- 
stance is made use of by the clover or pea, as the case may be. This is why 
such plants can thrive in soil with a poor nitrogen content. Later in the 
season some of the root tubercles die and decay. In this way some of the 
proteid substance is set free in the soil. The soil thus becomes richer in 
nitrogenous plant food. 

The forms of the bacteroids vary. In some of the clovers they are oval, 
in vetch they are rod-like or forked, and other forms occur in some of the 
other genera. 



320 



ECOLOG Y. 



Mycorhiza. 

603. Many others of the higher plants have fungi associated with their 
roots. Such roots are mycorhiza. In some genera of the orchids the roots 
form a compact mass resembling coral growth, as in the coral-root orchid. 
The curious Indian-pipe (monotropa) has roots which form a large closely 
branched mass of thickened short roots. In these cases the fungus lives in 








m 




ff] 




"fN 




1 7 




t^r^ 




/ 




3©)^ 


If 


t 




HRl ( * 




toili » 




. it - 


v$$m i: 






IkJ^Vi 




* * ! 


M 




■B^HEHSp 


S-. ■ ^ 



Fig. 423. 
Dodder. 

the cells of the root and some of the threads of the fungus extend to the 
outside into the soil, and perhaps partly serve as absorbent organs since the 
root hairs are very rare or altogether absent on such roots. The Indian- 
pipe plant possesses no chlorophyll, the fungus in its roots probably assimi- 
late- carbonaceous Good from decaying organic mutter in the soil, and gives 
it u]) to its host. 

604. Mycorhiza with the fungus in the roots are endotropic mycorhiza* 
The root tubercles of the legumes also belong to this class. EcUttroplC my- 



NUTRITION: MVCORHlZA. 321 

corhiza have the fungus on the outside of the roots. These often occur on 
the roots of the oak, beech, hornbeam, etc., in forests where there is a great 
deal of humus from the decaying leaves and other vegetation. The young 
growing roots of the oak. beech, horn beam, etc., become closely covered 
with a thick felt of the mycelium, so that no root hairs can develop. The 
root is also thickened. The fungus serves here as the absorbent organ for 
the tree. It also acts on the humus, converting it into available plant food 
and transferring it over to the tree. 

605. Nutrition of the dodder. — The dodder (cuscuta) is an example of one 
of the higher plants that is parasitic. The stem twines around the stems of 
other plants, sending haustoria in their tissues. By means of these the nutri- 
ment is absorbed. 

606. Carnivorous plants. — Examples of these are tne well-known venus 
fly-trap and the common sundew. 

607. Nutrition of bacteria. — Bacteria are very minute plants, in the 
form of short rods, which are either straight or spiral, while some are 
minute spheres. They are widely distributed ; some cause diseases of plants 
and animals, others cause decay of organic matter, while still others play an 
important role in converting certain nitrogen compounds into an available 
form for plant food. They absorb their food through the surface of their 
body. They may be obtained in abundance for study in infusions of plants 
or of meats. 



CHAPTER XLVII. 

FURTHER STUDIES ON NUTRITION CONCLUDED. 









608. Nutrition of moulds. — In our study of mucor, as we have seen, the 

growing or vegetative part 
of the plant, the mycelium, 
lies within the substratum, 
which contains the food 
materials in solution, and the 
slender threads are thus 
bathed on all sides by them. 
The mycelium absorbs the 
watery solutions throughout 
the entire system of ramifica- 
tions. When the upright 
fruiting threads are devel- 
oped they derive the materials 
for their growth directly from 
the mycelium with which 
they are in connection. The 
moulds which grow on de- 
caying fruit or on other 
organic matter derive their 
nutrient materials in the same 
way. The portion of the 
mould which we usually see 
on the surface of these sub- 
stances is in general the fruit- 
ing part. The larger part 
of the mycelium lies hidden 
within the subtratum. 

609. Nutrition of para- 
Carnation rust on lea/and flower stem. From photo- sitic fungi. -Certain of the 
graph. fungi grow on or within the 

higher plants and derive their food materials from them and at their ex- 
pense. Such a fungus is called a parasite, and there area large number 

322 




XI ■ TUITION : FUNGI. 



323 



of these plants which are known as parasitic fungi. The plant at whose 
expense they grow is called the "host." 

One of these parasitic fungi, which it is quite easy to obtain in green- 
houses or conservatories during the autumn and winter, is the carnation 
rust (Uromyces caryophy ■//imts), since it breaks out in rusty dark brown 
patches on the leaves and stems of the carnation (see fig. 424). If we make 
thin cross sections through one of these spots on a leaf, and place them for a 




Fig. 425. 
Several teleutospores, showing the variations in form. 

few minutes in a solution of chloral hydrate, portions of the tissues of the 
leaf will be dissolved. After a few minutes we wash the sections in water on 
a glass slip, and stain them with a solution of eosin. If the sections were care- 




Fig. 426. 
Cells from the stem of a rusted carnation, showing the intercellular mycelium and haustoria. 
Object magnified 30 times more than the scale. 

fully made, and thin, the threads of the mycelium will be seen coursing be- 
tween^the cells of the leaf as slender threads. Here and there will be seen 
short branches of these threads which penetrate the cell wall of the host and 
project into the interior of the cell in the form of an irregular knob. Such 
a branch is a haustorium. Bv means of this haustorrum, which is here 










3^4 



ECOLOGY. 



only a short branch of the mycelium, nutritive substances are taken by the 
fungus from the protoplasm or cell-sap of the carnation. From here it 
passes to the threads of the mycelium. These in turn supply food material 
for the development of the dark brown gonidia, which we see form the dark- 
looking powder on the spots. Many other fungi form haustoria, which take 
up nutrient matters in the way described for the carnation rust. In the case 




Fig. 427. 
Cell from carnation leaf, showing 
haustorium of rust mycelium grasping 
the nucleus of the host, h, haustori- 
um ; n, nucleus of host. 



Fig. 428. 
Intercellular mycelium with haustoria entering 
the cells. A , of Cystopus candidus (white rust) ; 
/>, of Peronospora calotheca. (De Bary.) 



of other parasitic fungi the threads of the mycelium themselves penetrate 
the cells of the host, while in still others the mycelium courses only between 
the cells of the host (fungus of peach leaf-curl for example) and derives food 
materials from the protoplasm or cell -sap of the host by the process of 
osmosis. 

610. Nutrition of the larger fungi. — If we select some one 
of the larger fungi, the majority of which belong to the mush- 
room family and its relatives, which is growing on a decaying log 
or in the soil, we shall see on tearing open the log, or on remov- 
ing the bark or part of the soil, as the case may be, that the 
stem of the plant, if it have one, is connected with whitish 
strands. During the spring, summer, or autumn months, exam- 
ples of the mushrooms connected with these strands may usually 
be found readily in the fields or woods, but during the winter and 



NUTRITION : FUNGI 



3^5 



colder parts of the year often they may be seen in forcing houses, 
especially those cellars devoted to the propagation of the mush- 
room of commerce. 

611. These strands are made up of numerous threads of the 
mycelium which are closely twisted and interwoven into a cord 
or strand, which is called a mycelium strand, or rhizomorph. 
These are well shown in fig. 434, which is from a photograph of 
the mycelium strands, or "spawn " as the grower of mushrooms 
calls it, of Agaricus campestris. The little knobs or enlargements 
on the strands are the young fruit bodies, or "buttons." 

612. While these threads or strands of the mycelium in the 
decaying wood or in the decaying organic matter of the soil are 




Fig. 429. 

Sterile mycelium on wood props in coal mine, 400 feet below surface, 
the author.) 



(Photographed by 



326 ECOLOGY, 

not true roots, they function as roots, or root hairs, in the ab- 
sorption of food materials. In old cellars and on damp soil in 
moist places we sometimes see fine examples of this vegetative 
part of the fungi, the mycelium. But most magnificent examples 
are to be seen in abandoned mines where timber has been taken 
down into the tunnels far below the surface of the ground to 
support the rock roof above the mining operations. I have 
visited some of the coal mines at Wilkesbarre, Ea., and here on 
the wood props and doors, several hundred feet below the surface, 
and in blackest darkness, in an atmosphere almost completely 
saturated at all times, the mycelium of some of the wood-destroy- 
ing fungi grows in a profusion and magnificence which is almost 
beyond belief. Fig. 429 is from a flash-light photograph of a 
beautiful example 400 feet below the surface of the ground. 
This was growing over the surface of a wood prop or post, and 
the picture is much reduced. On the doors in the mine one can 
see the strands of the mycelium which radiate in fan-like figures 
at certain places near the margin of growth, and farther back the 
delicate tassels of mycelium which hang down in fantastic figures, 
all in spotless white and rivalling the most beautiful fabric in the 
exquisiteness of its construction. 



Studies of mushrooms. 






613. Form of the mushroom. — A good example for this 
study is the common mushroom (Agaricus campestris) . 

This occurs from July to November in lawns and grassy fields. 
The plant is somewhat umbrella-shaped, as shown in fig. 430, 
and possesses a cylindrical stem attached to the under side of the 
convex cap or pileus. On the under side of the pileus are thin 
radiating plates, shaped somewhat like a knife blade. These are 
the gills, or lamellae, and toward the stem they are rounded on 
the lower angle and are not attached to the stem. The longer 
ones extend from near the stem to the margin of the pileus, and 
the V-shaped spaces between them are occupied by successively 



NUTRITION: MUSHROOMS. 



327 




Fig. 430. 
Agaricus campestris. View of under side showing stem, annulus, gills, and margin of pileus. 




Fig- 43i- 
Agaricus campestris. Longitudinal section through stem and pileus. a, pileus; b, portion 
of veil on margin of pileus ; c, gill ; /, fragment of annulus ; e, stipe. 



328 



ECOLOGY. 



shorter ones. Around the stem a little below the gills is a collar, 
termed the ring or annulus. 

614. Fruiting surface of the mushroom. — The surface of 
these gills is the fruiting surface of the mushroom, and bears the 
gonidia of the mushroom, which are dark purplish brown when 
mature, and thus the gills when old are dark in color. If we make 
a thin section across a few of the gills, we see that each side of 
the gill is covered with closely crowded club-shaped bodies, each 
one of which is a basidium. In fig. 432 a few of these are en- 

I ( t larged, so that the 
structure of the gill 
can be seen. Each 
basidium of the com- 
mon mushroom has 





Fig. 432. 
Portion of section of lamella of Agaricus campestris. 
tr f trama ; s/i, subhymenium ; />, basidium; st, sterigma 
(//. sterigmata) ; g t gonidium. 



^ig- 433- 
Portion of hymenium of Co- 
prinus micaceus, showing large 
cystidium in the hymenium. 



two spinous processes at the free end. Each one is a sierig'ma 
(plural slerig'mala), and bears a gonidium. In a majority of the 
members of the mushroom family each basidium bears four gonidia. 
When mature these gonidia easily fall away, and a mass of them 
gives a purplish-black color to objects on which they fall, so that 
a print of the under surface of the cap showing the arrangement 
of the gills can be obtained by cutting off the stem, and placing 
the pileus on white paper for a time. 

615, How the mushroom is formed. — The mycelium of the 



NUTRITION : MUSI/ROOMS. 







Pf§»l 




I^^PiSI 






m 


pPSflPw^ 


WM 










H^V K^S* V ^ iitfm ' 




■2 P^£^^| 




^Jgji JL. 





330 



ECOLOGY. 



mushroom lives in the ground, and grows here for several months 
or even years, and at the proper seasons develops the mature 
mushroom plant. The mycelium lives on decaying organic mat- 
ter, and a large number of the threads grow closely together form- 
ing strands, or cords, of mycelium, which are quite prominent 
if they are uncovered by removing the soil, as shown in fig. 434. 
616. From these strands the buttons arise by numerous threads 
growing side by side in a vertical direction, each thread growing 
independently at the end, but all lying very closely side by 




Fig- 435- 
Agaricus campestris ; sections of "buttons" of different sizes, showing formation of gills 
and veil covering them. 

side. When the buttons are quite small the gills begin to form 
on the under margin of the knob. They are formed by certain 
of the threads growing downward in radiating ridges, just as many 
of these ridges being started as there are to be gills formed. At 
the same time, threads of the stem grow upward to meet those at 
the margin of the button in such a manner that they cover up 
the forming gills, and thus enclose the gills in a minute cavity. 
Sections of buttons at different ages will show this, as is seen 
in fig. 435. This curtain of mycelium which is thus stretched 
a< ross the gill cavity is the veil. As the cap expands more 
and more this is stretched into a thin and delicate texture as 



NUTRITION: MUSHROOMS. 



331 



shown in fig. 436. Finally, as shown in fig. 437, this veil is 
ruptured by the expansion of the pileus, and it either clings 




Fig. 436. 
Agaricus campestris ; nearly mature plants, showing veil still stretched across the gill 
cavity. 




Fig. 437- 
Agaricus campestris ; under view of two plants just after rupture of veil, fragments of the 
latter clinging both to margin of pileus and to stem. 



332 



ECOLOG Y. 









Fig. 438. 

Agaricus campestris ; plant in natural position just after rupture of veil, showing tendency 
to double annulus on the stem. Portions of the veil also dripping from margin of pileus. 




Fig. 439. 

Agaricus campestris ; spore print. 



NUTRITION ■ MUSHROOMS. 



333 



9 

■1- *sj 







334 



ECOLOG Y. 



to the stem as a collar, or a portion of it remains clinging to 
the margin of the cap. When the buttons are very young 
the gills are white, but they soon become pink in color, and 




Fig. 44 i. 
Amanita phalloides ; white form, showing pileus, stipe, annulus, and volva. 

very soon after the veil breaks the gonidia mature, and then 
the gills are dark brown. 

617. Beware of the poisonous mushroom. — The number of 
species of mushrooms, or toadstools as they are often called, is 
very great. Besides the common mushroom ( Agaricus campes- 



NUTRITION : MUSHROOMS. 



335 



tris) there are a large number of other edible species. But 
one should be very familiar with any species which is gathered 
for food, unless collected by one who certainly knows what the 
plant is, since carelessness in this respect sometimes results fatally 
from eating poisonous ones. 

618. A plant very similar in structure to the Agaricus campes- 
tris is the Lepiota naucina, but the spores are white, and thus the 
gills are white, except that in age they become a dirty pink. 
This plant occurs in grassy fields and lawns often along with the 




Fig. 442. 
Amanita phalloides : plant turned to one side, after having been placed in a horizontal 
position, by the directive force of gravity. 



common mushroom. Great care should be exercised in collect- 
ing and noting the characters of these plants, for a very deadly 
poisonous species, the deadly amanita (Amanita phalloides) is 
perfectly white, has white spores, a ring, and grows usually in 
wooded places, but also sometimes occurs in the margins of lawns. 
In this plant the base of the stem is seated in a cup-shaped struc- 
ture, the volva, shown in fig. 441. One should dig up the stem 
carefully so as not to tear off this volva if it is present, for with 
the absence of this structure the plant might easily be mistaken 
for the lepiota, and serious consequences would result, 



33^ ECOLOGY. 

619. Wood-destroying fungi. — Several thousand different 
spe< ies of mushrooms are known in different countries. A large 
number of them grow in the soil, deriving their nutriment from 
decaying organic matter in the soil. ( Others grow in decaying 

DO o J O 

logs and plant parts. Still quite a large number of the mush- 
rooms and their relatives arc able to grow in the woody portions 
of the trunks of living trees, causing decay of the trunks. Still 
others are' parasitic. The wood-destroying fungi not only do 
great damage in destroying the usefulness of some timber trees 
for lumber, but they often so weaken the tree trunk or roots of 
the tree that the trees are broken down during gales. 

G20. The mycelium enters the tree at wounds in the trunk, 
limbs, or roots. A limb of a tree broken during a heavy wind, 
or by falling trees, or by the weight of snow , makes an infection 
court for the mycelium. A falling tree may bruise and knock off 
the bark from a sound standing tree and thus open a way for the 
entrance of the wood destroying mycelium. The routs of trees 
ate sometimes injured by the wheels of passing vehicles. In some 
cases 1 have known fungi to enter through such injuries. Shade 
trees an also similarly injured as well by the gnawing of animals 
when allowed to stand near them. Severe pruning of man)- large 
limbs of l ires often renders them liable to injury from the attacks 
of wood destroying fungi, since the small amount o\ leaf surface 
remaining is too little for the manufacture of die necessary plant 
food for repair of the wounds. .\ few limbs should be taken off 
in a single season w hen ne< essarj to prune, and extend the pro* 
ess over several seasons, rather than to prune so severely in a 
single season. 

621. From our studies on the growth in thi< kness oi woody 

Stems we know that the living and growing pari of a tree trunk 

is confined t<> .1 layer just underneath the bark. So when a 
bruise or break | >asse i through this layer (cambium 1 and exposes 
t he wood within, the mycelium oi the wood destroying fungi can 
easil) enter. From this point it spreads for long distances in the 
interior of the tree, causing decay. frees thus often become 
1 • hollow." Some oi die topmost branches die. The mycelium 



NUTRITION : MUSHROOMS. 



337 




Fig- 443- 
Wood-destroying fungus ( Hydnum septentrionale on living maple, reduced 1/15. (PhotQ- 
graph by the author. ) 



338 ECOLOG Y. 

eventually makes its way to the outside of the tree trunk in 
places, where large fruit bodies characteristic of the species are 
found. Figure 443 represents a large sugar-maple tree which is 
attacked by one of the wood-destroying fungi. The fruit bodies 
here are of the shelving form and overlap. The fruiting surface 
of this plant on the sugar maple is in the form of spines, instead 
of gills, and belongs to the genus hydnum. A number of large 
maple trees in the grove where this one stood were injured by 
wood-destroying fungi, and many of them were so weakened 
thereby that they were blown over during a southeast gale. 
Some shelving fungi possess gills like agaricus. Others have 
the under surface honeycombed as in polyporus. 

622. The roots of trees are often attacked by a mushroom, the 
honey agaric (Agaricus melleus). The mycelium here forms 
long black strands underneath the bark of the root. These often 
extend from the roots up into the interior of the trunk of the 
tree, causing decay. The roots are sometimes so weakened by 
the fungus that they die and easily break when heavy winds arise. 
Figure 444 shows such a tree uprooted. Further, it is broken 
about midway of the trunk, because the trunk was weakened 
by the mycelium inside. Other trees weakened by fungi, and 
broken over during the same gale, are shown in the same figure. 






NUTRITION: MUSHROOMS. 



339 



EL 






Si 3 

< O 4,. 



g, PL 




CHAPTER XLVIII. 

DIMORPHISM OF FERNS. 

623. In comparing the different members of the leaf series 
there are often striking illustrations of the transition from one 
form to another, as we have noted in the case of the trillium 
flower. This occurs in many other flowers, and in some, as in 
the water lily, these transformations are always present, here 
showing a transition from the petals to the stamens. In the bud 
scales of many plants, as in the butternut, walnut, currant, etc., 
there are striking gradations between the form of the simple bud 
scales and the form of the leaf. Some of the most interesting of 
these transformations are found in the dimorphic ferns. 

624. Dimorphism in the leaves of ferns. — In the common 
polypody fern, the maidenhair, and in many other ferns, all the 
leaves are of the same form. That is, there is no difference be- 
tween the fertile leaf and the sterile leaf. On the other hand, in 
the case of the Christmas fern we have seen that the fertile 
leaves are slightly different from the sterile leaves, the former 
having shorter pinnae on the upper half of the leaf. The fertile 
pinnae arc here the shorter ones, and perform but little of the 
function of carbon conversion. This function is chiefly per- 
formed by the sterile leaves and by the sterile portions of the 
fertile leaves. 'Ill is is a short step toward the division of labor 
between the two kinds of leaves, one performing chiefly the labor 
of carbon conversion, the other chiefly the labor of bearing the 
fru i t . 

625. The sensitive fern. — This division of labor is carded to 
an extreme extent in the case of some ferns. Some of our native 

340 



DIMORPHISM OF FERNS. 



341 



ferns are examples of this interesting relation between the leaves 
like the common sensitive fern (Onoclea sensibilis) and the 
ostrich fern (O. struthiopteris) and the cinnamon fern (Osmunda 
cinnamomea). The sensitive fern is here shown in fig. 445. 
The sterile leaves are large, broadly expanded, and pinnate, the 




Fig. 445- 
Sensitive fern ; normal condition of vegetative leaves and sporophylls. 

pinnae being quite large. The fertile leaves are shown also in 
the figure, and at first one would not take them for leaves at all. 
But if we examine them carefully we see that the general plan 
of tl^| leaf is the same : the two rows of pinnae which are here 
much shorter than in the sterile leaf, and the pinnules, or smaller 



342 



ECOLOG V. 



divisions of the pinnae, are inrolled into little spherical masses 
which lie close on the side of the pinnae. If we unroll one of 
these pinnules we find that there are several fruit dots within 
protected by this roll. In fact when the spores are mature these 




Fig. 446. 
Sensitive fern ; one fertile leaf nearly changed to vegetative leaf. 

pinnules open somewhat, so that the spores may be dissemi- 
nated. 

There is very little green color in these fertile leaves, and 
what green surface there is is very small compared with that of 
the broad expanse of the sterile leaves. So here there is practi- 
cally a complete division of labor between these two kinds of 



DIMORPHISM OF FERNS. 



343 



leaves, the general plan of which is the same, and we recognize 
each as being a leaf. 

626. Transformation of the fertile leaves of onoclea to 
sterile ones. — It is not a very rare thing to find plants of the 
sensitive fern which show intermediate conditions of the sterile 
and the fertile leaf. A number of years ago it was thought by 
some that this represented a different species, but now it is known 




Fig. 447. 
Sensitive fern, showing one vegetative leaf and two sporophylls completely transformed. 



that these intermediate forms are partly transformed fertile leaves. 

It is a very easy matter in the case of the sensitive fern to pro- 
i duce these transformations by experiment. If one in the spring, 

when the sterile leaves attain a height of 12 to 16 cm (8-10 

inches), cuts them away, and again when they have a second 
I time reached the same height, some of the fruiting leaves which 

develop later will be transformed. A few years ago I cut off the 



344 



ECOLOGY, 



sterile leaves from quite a large patch of the sensitive fern, once 
in May, and again in June. In July, when the fertile leaves 
were appearing above the ground, many of them were changed 
partly or completely into sterile leaves. In all some thirty plants 



s 




fp 


L 


" , %JWl^ 


W^w^*\ 



Fig. 448. 
Normal and transformed sporophyll of sensitive fern. 

showed these transformations, so that every conceivable gradation 
was obtained between the two kinds of leaves. 

627. It is quite interesting to note the form of these changed 
Leaves carefully, to sec how this change lias affected the pinnae 
and the sporangia. We note that the tip of the leaf as well as 
the tips of all the pinna' are more expanded than the basal por- 






DIMORPHISM OF FERNS. 345 

tions of the same. This is due to the fact that the tip of the 
leaf develops later than the basal portions. At the time the 
stimulus to the change in the development of the fertile leaves 
reaehed them they were partly formed, that is the basal parts of 
the fertile leaves were more or less developed and fixed and 
could not change. Those portions of the leaf, however, which 
were not yet completely formed, under this stimulus, or through 
correlation of growth, are incited to vegetative growth, and ex- 
pand more or less completely into vegetative leaves. 

628. The sporangia decrease as the fertile leaf expands. — 
If we now examine the sporangia on the successive pinnae of a 
partly transformed leaf we find that in case the lower pinnae are 
not changed at all, the sporangia are normal. But as we pass to 
the pinnae which show increasing changes, that is those which are 
more and more expanded, we see that the number of sporangia 
decrease, and many of them are sterile, that is they bear no 
spores. Farther up there are only rudiments of sporangia, until 
on the more expanded pinnae sporangia are no longer formed, 
but one may still see traces of the indusium. On some of the 
changed leaves the only evidences that the leaf began once to 
form a fertile leaf are the traces of these indusia. In some of 
these cases the transformed leaf was even larger than the sterile 
leaf. 

629. The ostrich fern. — Similar changes were also produced 
in the case of the ostrich fern, and in fig. 448 is shown at the 
left a normal fertile leaf, then one partly changed, and at the 
right one completely transformed. 

630. Dimorphism in tropical ferns. — Very interesting forms 
of dimorphism are seen in some of the tropical ferns. One of 
these is often seen growing in plant conservatories, and is known 
as the staghorn fern (Platy cerium alcicorne). This in nature 
grows attached to the trunks of quite large trees at considerable 
elevations on the tree, sometimes surrounding the tree with a 
massive growth. One kind of leaf, which may be either fertile 
or sterile, is narrow, and branched in a peculiar manner, so that 
it resembles somewhat the branching of the horn of a stag 



346 



ECOLOGY. 



Below these are other leaves which are different in form and 
sterile. These leaves are broad and hug closely around the roots 
and bases of the other leaves. Here they serve to catch and 




Ostrich fern 
transformed. 



Fig. 449. 
showing one normal sporophyll, one partly transformed, and one completely 



retain moisture, and they also catch leaves and other vegetable 
matter which falls from the trees. In this position the leaves 
decay and then serve as food for the fern. 



CHAPTER XLIX. 

FORMATION OF EARLY SPRING FLOWERS. 

631. Trillium. — As this white flower with its setting of green 
sepals is glinting to us out of copses and woodland like so many 
new fairies, few of us realize the long task which it has already 
begun in the silent depths of the soil in order that it may suddenly 
blossom again in season, when springtime returns. If we re- 
move the old scales where the flowering stem joins the root-stock, 
we will see a pointed, conical, white bud, which is to develop 
into the next season's leafy plant and blossom. From June to 
August the new leaves and flower are slowly forming, protected 
by several overlapping, thick, whitish, soft scales, which form a 
conical roof to keep out water, and to protect against too sudden 
changes in cold during the autumn and winter season. In Sep- 
tember we find that leaves and sepals are well formed and green, 
the petals are already white, and within are the six stamens and 
the angular pistil, all well formed. Where the sun reaches these 
copses and warms the soil well in autumn, sometimes the stamens 
are yellowish as early as September or October from the already 
formed pollen. In the cooler shades the pollen is not yet formed 
and the stamens remain whitish in color. But with the first onset 
of warm weather in the spring, or on warm days in the winter, 
before the flower bud lifts its head from its long winter sleep, 
snugly ensconced among the fallen leaves or spongy humus, the 
pollen quickly forms. Now all the plant has to do is to erect 
its standard, bearing aloft the opening blossom. 

632. The ovules, begun in the autumn, are now being com- 
pleted, pollenation takes place, and later fertilization, and the 
embryo begins to form in June, The pure white flowers soon 

347 



34« 



ECOLOG V 




E - 



EARLY SPRING F10 1VERS. 349 

. change to pinkish, the first evidence of decline. Finally they 
wither, and during the summer the fruit and seed are formed on 
the old flower stem, while the secret formative processes of the 
new blossoms are going on anew. 

633. The adder-tongue (erythronium) comes out early in 
the spring to catch the sunlight gleaming through rifts in the 
woodland. It is not so forbidding as its name or its " darting " 
style would suggest. The rich color of its curved petals nodding 
from the fork of the variegated leaves lends cheer and brightness 
to the gray carpet of forest leaves. We are apt to associate the 
formation of the flower with the early springtime. But after the 
flower perishes, the bulb, deep in the soil, slowly builds the next 
season's flower, which is kept through the autumn and winter, 
much of the time encased in ice, waiting for springtime that it 
may rise and unfold. 

634. Indian-turnip. — The "Indian-turnip," or " jack-in-the- 
pulpit " (Arissema triphyllum), loves the cool, shady, rich, allu- 
vial soil of low grounds, or along streams, or on moist hillsides. 
A group of the jacks is shown in figure 45 7 as they occur in the 
rich soil on dripping rocks in one of our glens. At their feet is 
a carpet of moss. Often the violet sits humbly underneath its 
spreading three-parted leaves. The thin, strap-shaped spathe, 
unfolded at its base, bends gracefully over the spadix, the sterile 
end of which stands solitary in the pulpit thus formed. The 
flowers are very much reduced, and the plants are " dimorphic " 
usually. 

635. Female plants. — The large plants usually bear the pistil- 
late flowers, which are clustered around the base of the spadix, 
each flower consisting of a single pistil, oval in form, terminat- 
ing in a brush-like stigma. The stigma consists of numerous 
spreading, delicate hairs. The open cavity of' the short style is 
hairy also, and a brush of hairs extends into the cavity of the ovary. 
Into this brush of internal hairs the necks of the several ovules 
crowd their way to the base of the style near its opening. Even 
when the stigma is not pollenated the ovary continues to grow in 
size, and the stigmatic brush remains fresh for a long time. 



35° ECOLOGY. 

636. Male plants. — Excepting some of the intermediate sizes, 
one can usually select on sight the male and female plants. The 
smaller ones which have a spathe are nearly all male and bear a 
single leaf, though a few have two leaves. The male flowers are 
also clustered at the base of the spadix, and are very much 
reduced. Each flower consists only of stamens, and singularly 
the stamens of each flower are joined into one compound stamen, 
the anther-sacs forming rounded lobes at the end of the short 
consolidated filaments. 

637. In some plants both male and female flowers occur on a 
single spadix, the lower flowers being female, while the upper 
ones are male. The larger plants are nearly all female, and many, 
though not all, bear two leaves. In this dimorphism of the plant 
there is a division of labor apportioned to the destiny and needs 
of each, and in direct correspondence with the capacity to supply 
nutriment. The staminate flowers, being short-lived, need com- 
paratively a small amount of nutriment, and after the escape of 
the pollen (dehiscence of the anthers) the spathe dies, while the 
leaf remains green to assimilate food for growth of the fleshy short 
stem (corm), where also is stored nutriment for the growth in the 
autumn and spring when the leaf is dead. The female plants 
have more work to do in providing for the growth of the embryo 
and seed, in addition to the growth of the corm and next season's 
flower. The smaller female plants thus sometimes exhaust them- 
selves so in seed bearing that the corm becomes small, and the 
following season the plant is reduced to a male one. 

638. The new roots each year arise from the upper part of the 
corm. The stored substances in the base of the corm are used 
in the early season's growth, and the old tissue sloughs off as the 
new corm is formed above upon its remains. 









CHAPTER L. 



POLLENATION. 

Origin of heterospory, and the necessity for 
pollenation. 

639. Both kinds of sexual organs on the same prothallium. — In the ferns, as 
we have seen, the sexual organs are borne on the prothallium, a small, leaf-like, 
heart-shaped body growing in moist situations. In a great many cases both 
kinds of sexual organs are borne on the same prothallium. While it is per- 
haps not uncommon, in some species, that the egg cell in an archegonium 
may be fertilized by a spermatozoid from an antheridium on the same pro- 
thallium, it happens many times that it is fertilized by a spermatozoid from 
another prothallium. This may be accomplished in several ways. In the 
first place antheridia are usually found much earlier on the prothallium than 
are the archegonia. When these antheridia are ripe, the spermatozoids es- 
cape before the archegonia on the same prothallium are mature. 

640. Cross fertilization in monoecious prothallia. — By swimming about in 
the water or drops of moisture which are at times present in these moist situa- 
tions, these spermatozoids may reach and fertilize an egg which is ripe 
in an archegonium borne on another and older prothallium. In this way 
what is termed cross fertilization is brought about nearly as effectually as if 
the prothallia were dioecious, i.e. if the antheridia and archegonia were all 
borne on separate prothallia. 

641. Tendency toward dioecious prothallia. — In other cases some fern pro- 
thallia bear chiefly archegonia, while others bear only antheridia. In these 
cases cross fertilization is enforced because of this separation of the sexual 
organs on different prothallia. These different prothallia. the male and 
female, are largely due to a difference in food supply, as has been clearly 
proven by experiment. 

612. The two kinds of sexual organs on different prothallia. — In the horse- 
tails (equisetum) the separation of the sexual organs on different prothallia has 
become quite constant. Although all the spores are alike, so far as we can 
determine, some produce small male plants exclusively, while others produce 

351 




352 ECOLOGY. 

large female plants, though in some cases the latter bear also antheridia. It 
has been found that when the spores are given but little nutriment they form 
male prothallia, and the spores supplied with abundant nutriment form 
female prothallia. 

643. Permanent separation of sexes by different amounts of nutriment sup- 
plied the spores. — This separation of the sexual organs of different prothallia, 
which in most of the ferns, and in equisetum, is dependent on the chance 
supply of nutriment to the germinating spores, is made certain when we come 
to such plants as isoetes and selaginella. Here certain of the spores receive 
more nutriment while they are forming than others. In the large sporangia 
(macrosporangia) only a few of the cells of the spore-producing tissue form 
spores, the remaining cells being dissolved to nourish the growing macro- 
spores, which are few in number. In the small sporangia (microsporangia) 
all the cells of the spore-producing tissue form spores. Consequently each 
one has a less amount of nutriment, and it is very much smaller, a micro- 
spore. The sexual nature of the prothallium in selaginella and isoetes, then, is 
predetermined in the spores while they are forming on the sporophyte. The 
microspores are to produce male prothallia, while the macrospores are to 
produce female prothallia. 

644. Heterospory. — This production of two kinds of spores by isoetes, 
selaginella, and some of the other fern plants is heterospory, or such plants 
are said to be heterosporons. Heterospory, then, so far as we know from liv- 
ing forms, has originated in the fern group. In all the higher plants, in the 
gymnosperms and angiosperms, it has been perpetuated, the microspores being 
represented by the pollen, while the macrospores are represented by the em. 
bryo sac; the male organ of the gymnosperms and angiosperms being the 
antherid cell in the pollen or pollen tube, or in some cases perhaps the pollen 
grain itself, and the female organ in the angiosperms perhaps reduced to 
the egg cell of the embryo sac. 

645. In the pteridophytes water serves as the medium for conveying the 
sperm cell to the female organ.- — In the ferns and their allies, as well as in 
the liverworts and mosses, surface water is a necessary medium through 
which the generative or sperm cell of the male organ, the spermatozoid, may 
reach the germ cell of the female organ. The sperm cell is here motile. 
This is true in a large number of eases in the algae, which arc mostly aquatic 
plants, while in other cases currents of water float the sperm cell to the 
female organ. 

646. In the higher plants a modification of the prothallium is necessary. 
— As we pass to the gymnosperms and angiosperms, however, where the 
primitive phase (the gametophyte) of the plants has become dependent solely 
on the modern phase (the sporophyte) of the plant, surface water no longer 
serves as the medium through which a motile sperm cell reaches the egg cell 
to fertilize it. The female prothallium, or macrospore, is, in nearly all 



POLLENATION: heterospory. 353 

cases, permanently enclosed within the sporangium, so that if there were 
motile sperm cells on the outside of the ovary, they could never reach the 
egg to fertilize it. 

647. But a modification of the microspore, the pollen tube, enables the 
sperm cell to reach the egg cell. The tube grows through the nucellus, 
or first through the tissues of the ovary, deriving nutriment therefrom. 

648. But here an important consideration should not escape us. The pol- 
len grains (microspores) must in nearly all cases first reach the pistil, in 
order that in the growth of this tube a channel may be formed through which 
the generative cell can make its way to the egg cell. The pollen passes from 
the anther locule, then, to the stigma of the ovary. This process is termed 
pollenation. 



Pollenation. 

649. Self pollenation, or close pollenation. — Perhaps very few of the ad- 
mirers of the pretty blue violet have ever noticed that there are other flowers 
than those which appeal to us through the beautiful colors of the petals. 
How many have observed that the brightly colored flowers of the blue violet 
rarely " set fruit " ? Underneath the soil or debris at the foot of the plant 
are smaller flowers on shorter, curved stalks, which do not open. When the 
anthers dehisce, they are lying close upon the stigma of the ovary, and the 
pollen is deposited directly upon the stigma of the same flower. This 
method of pollenation is self 'pollenation, or close pollenation. These small, 
closed flowers of the violet have been termed " cleistogamons" because thev 
are pollenated while the flower is closed, and fertilization takes place as a 
result. 

But self pollenation takes place in the case of some open flowers. In some 
cases it takes place by chance, and in other cases by such movements of the 
stamens, or of the flower at the time of the dehiscence of the pollen, that it 
is quite certainly deposited upon the stigma of the same flower. 

650. Wind pollenation. — The pine is an example of wind pollenated flowers. 
Since the pollen floats in the air or is carried by the "wind," such flowers 
are anemophilons. Other anemophilous flowers are found in other conifers, 
in grasses, sedges, many of the ament-bearing trees, and other dicotyledons. 
Such plants produce an abundance of pollen and always in the form of 
"dust," so that the particles readily separate and are borne on the wind. 

651. Pollenation by insects. — A large number of the plants which we have 
noted as being anemophilous are monoecious or dioecious, i.e. the stamens 
and pistils are borne in separate flowers. The two kinds of flowers thus formed, 
the male and the female, are borne either on the same individual (monoe- 
cious) or on different individuals (dioecious). In such cases cross pollenation, 



354 



ECOLOGY. 



i.e. the pollenation of the pistil of one flower by pollen from another, is 
sure to take place, if it is pollenated at all. Even in monoecious plants cross 
pollenation often takes place between flowers of different individuals, so that 







Fig- 45i- 
Viola cucullata ; blue flowers above, cleistogamous flowers smaller and curved below. 
Section of pistil at right. 

more widely different stocks are united in the fertilized egg, and the strain 
is kept more vigorous than if very close or identical strains were united. 

652. I > i i t there are many flowers in which both stamens and pistils are pres- 
ent, and yet in which cross pollenation is accomplished through the agency of 
inse< ts. 

653. Pollenation of the bluet. — In the pretty bluet the stamens and 
styles of the (lowers are of different length as shown in figures 452, 453. 
The stamens of the Long-styled flower are at about the same level as the 
stigma ot the short- styled flower, whil< the stamens of the latter are on 



POLLEXA TION: HF.TEROSPORY. 



355 



about the same level as the stigma of the former. What does this interesting 
relation of the stamens and pistils in the two different flowers mean ? As the 
butterfly thrusts its "tongue" down into the tube of the long-styled flower 





Fig. 452. 
Dichogamous flower of the bluet (Houstonia coerulea), the long-styled form. 

for the nectar, some of the pollen will be rubbed off and adhere to it. When 
now the butterfly visits a short-styled flower this pollen will be in the right 
position to be rubbed off onto the stigma of the short style. The positions of 





Fig. 453- 
Dichogamous flower of bluet (Houstonia coerulea), the short-styled form. 

the long stamens and long style are such that a similar cross pollenation will 
be effected. 

654. Pollenation of the primrose. — In the primroses, of which we have 
examples growing in conservatories, that blossom during the winter, we 
have almost identical examples of the beautiful adaptations for cross polle- 
nation by insects found in the bluet. The general shape of the corolla is 



356 



ECOLOQ Y. 



the same, but the parts of the flower are in fives, instead of in fours as in 
the bluet. While the pollen of the short-styled primulas sometimes must 
fall on the stigma of the same flower, Darwin has found that such pollen is 




Fig. 454- 
Dichogamous flowers of primula. 



not so potent on the stigma of its own flower as on that of another, an ad- 
ditional provision which tends to necessitate cross pollenation. 

In the case of some varieties of pear trees, as the bartlett, it has been 
found that the flowers remain largely sterile not only to their own pollen, or 
pollen of the flowers on the same tree, but to all flowers of that variety. 
However, they become fertile if cross pollenated from a different variety of 
pear. 

655. Pollenation of the skunk's cabbage. — In many other flowers cross 
pollenation is brought about through the agency of insects, where there is a 
difference in time of the maturing of the stamens and pistils of the same 
flower. The skunk's cabbage (Sphathyema fcetida), though repulsive on 
account of its fetid odor, is nevertheless a very interesting plant to study for 
several reasons. Early in the spring, before the leaves appear, and in many 
cases as soon as the frost is out of the hard ground, the hooked beak of the 
large fleshy spathe of this plant pushes its way through the soil. 

If we cut away one side of the spathe as shown in fig. 456 we shall have 
the flowering spadix brought closely to view. In this spadix the pistil of 
each Crowded flower ha- pushed its style through between the plates of 
armor formed by the converging ends of the sepals, and stands out alone 
with the brush-like stigma ready lor pollenation, while the stamens of all the 
flowers of this spadix arc yet hidden beneath. The insects which pass from 
the spadix of one plant to another will, in crawling over the projecting 
stigmas, nib off some of the pollen which has been caught while visiting a 
plant where the stamens .lit- scattering their pollen, [n this way cross pollen* 
ation is brought about. Such flowers, in which the stigma is prepared 



POLLEN A TION : HE TEROSPOR Y. 



357 




*'ig- 455- 
Skunk's cabbage. 







Fig. 456. 35S 

Proterogyny in skunk's cabbage. (Photograph by the author.) 



POLLENATION: HETEROSPORY. 359 




fig. 457- 
Skunk's cabbage ; upper flowers proterandrous, lower ones proterogynous. 



360 ECOLOG Y. 

for pollenation before the anthers of the same flower are ripe, are protcr- 
ogynous. 

656. Now if we observe the spadix of another plant we may see a condi- 
tion of things similar to that shown in fig. 457. In the flowers in the upper 
part of the spadix here the anthers are wedging their way through between 
the armor- like plates formed by the sepals, while the styles of the same 
flowers are still beneath, and the stigmas are not ready for pollenation. Such 
flowers are proterandrous, that is, the anthers are ripe before the stigmas of 
the same flowers are ready for pollenation. In this spadix the upper flowers 
are proterandrous, while the lower ones are proterogynous, so that it might 
happen here that the lower flowers would be pollenated by the pollen falling 
on them from the stamens of the upper flowers. This would be cross pol- 
lenation so far as the flowers are concerned, but not so far as the plants are 
concerned. In some individuals, however, we find all the flowers proter- 
androus. 

657. Spiders have discovered this curious relation of the flowers and in- 
sects. — On several different occasions, while studying the adaptations of the 
flowers of the skunk's cabbage for cross pollenation, I was interested to find 
that the spiders long ago had discovered something of the kind, for they 
spread their nets here to catch the unwary but useful insects. I have not 
seen the net spread over the opening in the spathe, but it is spread over the 
spadix within, reaching from tip to tip of either the stigmas, or stamens, or 
both. Behind the spadix crouches the spider-trapper. The insect crawls 
over the edge of the spadix, and plunges unsuspectingly into the dimly 
lighted chamber below, where it becomes entangled in the meshes of the 
net. 

Flowers in which the ripening of the anthers and maturing of the stigmas 
occur at different times are also said to be dichogamous. 

658. Pollenation of jack-in-the pulpit. — The jack-in-the-pulpit (Arissema 
triphyllum) has made greater advance in the art of enforcing cross pollena- 
tion. The larger number of plants here are, as we have found, dioecious, the 
staminate flowers being on the spadix of one plant, while the pistillate flowers 
are on the spadix of another. In a few plants, however, we find both 
female and male flowers on the same spadix. 

659. The pretty bellflower (Campanula rotundifolia) is dichogamous 
and proterandrous (fig. 459). Many of the composites are also dichoga- 
mous. 

660. Pollenation of orchids. — But some of the most marvellous adapta- 
tions for cross pollenation by insects are found in tin- orchids, or members of 
the orchis family. The Larger number of the members of this family grow 
in the tropics. Many of these in the forests are supported in lofty trees 
where they are brought near the sunlight, and such are called "epiphytes." 
A number of species of orchids are distributed in temperate regions. 



POLLENATION: HETEROSPORW 



361 



661. Cypripedium or lady-slipper. — One species of the lady-slipper is 

shown in fig. 465. The labellnm in this genus is shaped like .1 shoe, as one 




Fig. 458. 
A group of jacks. 



can see by the section of the flower in fig. 465. The stigma i< situated at sf, 
while the anther is situated at a, upon the style. The insect enters about 
the middle of the boat-shaped labellum. In going out it passes up and out 



362 



ECOLOGY. 



at the end near the flower stalk. In doing this it passes the stigma first and 
the anther last, rubbing against both. The pollen caught on the head of 





Fig- 459- 

Proterandry in the bell-flower (campanula). Left figure shows the svngencecious stamens 
surrounding the immature style and stigma. Middle figure shows the immature stigma being 
pushed through the tube and brushing out the pollen : while in the right-hand figure, after 
the pollen has disappeared, the lobes of the stigma open out to receive pollen from another 
flower. 

the insect, will not touch the stigma of the same flower, but will be in posi- 
tion to come in contact with the stigma of the next flower visited. 

662. Epipactis. — In epipactis, shown in fig. 466. the action is similar to 
that of the blue iris. 




Fig. 460. 

Kalinin Latifolia, showing position of anthers before insect visits, and at the right the 
scattering <>i tin. pollen when disturbed by insects. Middle figure section ol flower. 

663. In some of the tropical orchids the pollinia are set free when the insect 
touches a certain part of tin- flower, and are thrown iii such a way that the 
disk of the pollinium strike- the insect's head and stand- upright. By the 
time the insect reaches another flowed the pollinium has bent downward sufti- 



POLLEN A TLON : HE TEROSPOR V. 



363 



ciently to strike against the stigma when the insect alights on the labellum. 
In the mountains of North Carolina I have seen a beautiful little orchid, in 
which, if one touches a certain part of the flower with a Lead-pencil or other 
suitable object, the pollinium is set free suddenly, turns a complete somer- 
sault in the air, and lands with the disk sticking to the pencil. Many of the 




Fig. 461. 
Spray of leaves and flowers 
of cytisus. 



orchids grown in conservatories can be used to demonstrate some of these 
peculiar mechanisms. 

664. Pollenation of the carina. — In the study of some of the marvellous 
adaptations of flowers for cross pollenation one is led to inquire if, after all, 
plants are not intelligent beings, instead of mere automatons which respond 





Fig. 462. 
Flower of cytisus grown in conservatory. Same flower scattering poller. 



to various sorts of stimuli. No plant has puzzled me so much in this respect 
as the canna, and any one will be well repaid for a stud}' of recently opened 
flowers, even though it may be necessary to rise early in the morning to 
unravel the mystery, before bees or the wind have irritated the labellum. 
The canna flower is a bewildering maze of petals and petal-like members. 



3 6 4 



ECOLOGY. 



The calyx is green, adherent to the ovary, and the limb divides into three, 
lanceolate lobes. The petals are obovate and spreading, while the stamens 
have all changed to petal-like members, called staminodia. Only one still 
shows its stamen origin, since the anther is seen at one side, while the fila- 
ment is expanded laterally and upwards to form the staminodium. 




Fig. 463. 

Spartium, showing the dusting of the pollen through the opening keels on the under side 
of an insect. ( From kerner and ( )liver. 1 



665. The ovary lias three locales, and the three styles are usually united 
into a Long, thin, strap-shaped style, as seen in the figure, though in some 
cases three, nearly distinct, filamentous styles are present. The end of this 

strap-shaped style has a peculiar curve on one side-, the outline being some- 



POLLEN A TION : HE TEROSPOR V. 



365 



times like a long narrow letter S. It is on the end of this style, and along 
the crest of this curve, that the stigmatic surface lies, so that the pollen 




Fig. 465. 
Section of flower of cypripedium. st, 
stigma ; a, at the left stamen. The insect 
enters the labellum at the center, passes 
under and against the stigma, and out 
through the opening 6, where it rubs 
against the pollen. In passing through 
another flower this pollen is rubbed off 
on the stigma. 

must be deposited on the stigmatic end or margin 
in order that fertilization may take place. 

666. If we open carefully / canna-flower buds 
which are nearly ready to open naturally, by 
unwrapping the folded petals and staminodia, we will see the anther-bearing 



Fig. 464. 
Cypripedium. 




Fig. 466. 
Epipactis with portion of perianth removed to show details. /, labellum ; sf, stigma: r 
rostellum; /, pollinium. When the insect approaches the flower its head strikes the disk 
of the pollinium and pulls the pollinium out. At this time the pollinium stands up out of the 
way of the stigma. By the time the insect moves to another flower the pollinia have moved 
downward so that they are in position to strike the stigma and leave the pollen. At the 
right is the head of a bee, with two pollinia (a) attached." 



3 66 



ECO LOG Y. 



staminodium is so wrapped around the flattened style that the anther lies 
closely pressed against the face of the style, near the margin opposite that 
on which the stigma lies. 

667. The walls of the anther locules which lie against the style become 
changed to a sticky substance for their entire length, so that they cling 

firmly to the surface of the style 
and also to the mass of pollen 
within the locules. The result is 
that when the flower opens, and 
this staminodium unwraps itself 
from the embrace of the style, the 
mass of pollen is left there de- 
posited, while the empty anther is 
turned around to one side. 

668. Why does the flower de- 
posit its own pollen on the style ? 
Some have regarded this as the act 
of pollenation, and have concluded, 
therefore, that cannas are neces- 
sarily self pollenated, and that 
cross pollenation does not take 
place. But why is there such evi- 
dent care to deposit the pollen on 
the side of the style away from the 
stigmatic margin ? If we visit the 
cannas some morning, when a 
number of the flowers have just opened, and the bumblebees are humming 
around seeking ior nectar, we may be able to unlock the secret. 

669. We see that in a recently opened canna flower, the petal which 
directly faces the style in front stands upward quite close to it, so that the 
flower now is somewhat funnelshaped. This front petal is the labellum, and 
is the landing place for the bumblebee as he alights on the flower. Here 
he comes humming along and alights on the labellum with his head so close 
to tin- style that it touches it. But just the instant that the bee attempts to 
crowd down in the flower the labellum suddenly bends downward, as shown 
in fig. 468. Tn so doing the head of the bumblebee scrapes against the 
pollen, bearing some of it off. Now while the bee is sipping the nectar it is 
too Ear below the stigma to deposit any pollen on the latter. When the bum- 
blebee Hies to another newly opened flower, as it alights, some of the pollen 
of the former flower i- brushed on the stigma. 

670. One can easily demonstrate the sensitiveness of the labellum of 
recently opened (anna flowers, if the labellum has not already moved down 
in response to some stimulus. Take a lead-pencil, or a knife blade, or even 




Fig. 467. 

Canna flowers with the perianth removed to 
show the depositing of the pollen of the style by 
the stamen. 



POL LENA TION : HE TEKOSPQR ) . 



367 



the finger, and touch the upper surface of the labellum by thrusting it 
between the latter and the style. The labellum curves quickly downward. 

671. Sometimes the bumblebees, after sipping the nectar, will crawl up 
over the style in a blundering manner. In this way the flower may be pol- 



f"V\ 







Pollenation of the canna flower by bumblebee. 



Canna flower. Pollen on style, sta- 
men at left. 



lenated with its own pollen, which is equivalent to self pollenation. Un- 
doubtedly self pollenation does take place often in flowers which are adapted, 
to a greater or less degree, for cross pollenation by insects. 



CHAPTER LI. 



SEED DISTRIBUTION. 



672. Means for dissemination of seeds. — During Late summer or autumn 
a walk in the woods or afield often convinces us of the perfection and variety 

of means with which plants are provided for the dissemination of their 
seeds, especially when we discover that several hundred seeds or fruits of 
different plants are stealing a ride at our expense and annoyance. The hooks 
and barbs on various seed-pods catch into the hairs of passing animals and 
the seeds may thus be transported "^^m^ 
considerable distances. Among the 
plants familiar to us, which have such 
contrivances for unlawfully gaining 
transportation, are the beggar-ticks 
or stick tights, or sometimes called 





Fig I'"; 

Bur * » t bidens or bur marigold, show- 
ing barbed seeds. 



Fig. 470. 
Seed pod of tick-treefoil (desmodium) ; at the 
right some of the hooks greatly magnified. 



bur-marigold (bidens), the tick-treefoil (desmodium), or cockle-bur (xanthi- 
um), and burdock (arctium). 

673. Other plants like some of the sedges, etc., living on the margins of 
streams and oi lakes, have -teds which are provided with floats. The wind 
or the Bowing of the water transports fhem often to distant points. 

368 



SEED D 1ST NIB L ' TION. 



369 



674. Many plants possess attractive devices, and offer a substantial 
reward, as a price for the distribution oi their seeds. Fruits and berries art- 
devoured by birds and other animals ; the seeds within, often passing un- 
harmed, may be carried long distances. Starch}' and albuminous seeds and 





Fig. 47 1 . 
Seeds of geum showing the hooklets where the end of the style is kneed. 



grains are also devoured, and while many such seeds are destroyed, others 
are not injured, and finally are lodged in suitable places for growth, often 
remote from the original locality. Thus animals willingly or unwillingly 
become agents in the dissemination of plants over the earth. Man in the 
development of commerce is often responsible for the wide distribution of 
harmful as well as beneficial species. 

675. Other plants are more independent, and mechanisms are employed 
for violently ejecting seeds from the pod or fruit. The unequal tension of 
the pods of the common vetch (Vicia sativa) when drying causes the valves 
to contract unequally, and on a dry summer day the valves twist and pull in 
opposite directions until they suddenly snap apart, and the seeds are thrown 
forcibly for some distance. In the impatiens, or touch-me-not as it is better 
known, when the pods are ripe, often the least touch, or a pinch, or jar, sets 
the five valves free, they coil up suddenly, and the small seeds are whisked 
for several yards in all directions. During autumn, on dry days, the pods 
of the witch hazel contract unequally, and the valves are suddenly spread 
apart, when the seeds, as from a catapult, are hurled away. 

Other plants have learned how useful the ••wind"' may be if the seeds are 
provided with "floats," k * parachutes." or winged devices which buoy them 



37o 



ECOLOGY. 



up as they are whirled along, often miles away. In late spring or early 
summer the pods of the willow burst open, exposing the seeds, each with a 
tuft of white hairs making a mass of soft down. As the delicate hairs dry, 




Fig. 472. 
Touch-me-not (Impatiens fulva) ; side and front view of flower below ; above unopened 
pod, and opening to scatter the seed. 

they straighten out in a loose spreading tuft, which frees the individual seeds 
from the compact mass. Here they are caught by currents of air and float 
off singly or in small clouds. 

676. The prickly lettuce. — In late summer or early autumn the seeds of 
the prickly lettuce (La.ctuca scariola) are caught up from the roadsides by 
the winds, and carried to fields where they are unbidden as well as unwel- 
come guests. This plant is shown in fig. 473. 

677. The wild lettuce.- -A related species, the wild lettuce (Lactuca cana- 
densis) occurs on roadsides and in the borders of fields, and is about one 
meter in height. The heads of small yellow or purple flowers are arranged 
in a loose or branching panicle. The flowers are rather inconspicuous, the 
rays projecting but little above the apex of the enveloping involucral bracts, 
which closely press together, forming a flower-head more or less flask- 
shaped. 

At the time of flowering the involucral bracts spread somewhat at the 
apex, and the tips of the flowers are .1 little more prominent. As the flowers 
then wither, the bracts pre-- closely together again and the head is closed. 
As the seeds ripen the bracts die, and in drying bend outward and down- 
ward, hugging the flower stem below, br they fall away. The seeds are 



SEED DISTRIBUTION. 



371 



thus exposed. The dark brown achenes stand over the surface of the recep- 
tacle, each one tipped with the long slender beak of the ovary. The "pap- 
pus," which is so abundant in many of the plants belonging to the composite 
family, forms here a 

pencil-like tuft at the \>A ^ 

tip of this long beak. Vw^j' 

As the involucral bracts 
dry and curve down- 
ward, the pappus also 
dries, and in doing so 
bends downward and 
stands outward, brist- 
ling like the spokes of 
a fairy wheel. It is an 
interesting coincidence 
that this takes place 
simultaneously w i t h 
the pappus of all the 
seeds of a head, so 
that the ends of the 
pappus bristles of ad- 
joining seeds meet, 
forming a many-sided 
dome of a delicate and 
beautiful texture. This 
causes the beaks of the 
achenes to be crowded 
apart, and with the 
leverage thus brought to 
bear upon the achenes 
they are pried off the 
receptacle. They are 
thus in a position to 
be wafted away by the 
gentlest zephyr, and 
they go sailing away 
on the wind like a 
miniature parachute. 
As they come slowly 
to the ground the seed 
is thus carefully low- 
ered first, so that it touches the ground in a position for the end whicl 
contains the root of the embryo to come in contact with the soil. 




Fig. 473. 
Lactuca scariola. 



372 ECOLOGY. 

678. The milkweed, or silkweed.— The common milkweed, or silkweed 
(Asclepias cornuti), so abundant in rich grounds, is attractive not only 




Fig. 474. 
Milkweed (Asclepias cornuti) ; dissemination of seed. 

because of the peculiar pendent flower clusters, but also for the beautiful 
floats with which it sends its seeds skyward, during a puff of wind, to finally 
lodge on the earth. 

679. The large boat-shaped, tapering pods, in late autumn, .ire packed 
with oval, flattened, brownish seeds, which overlap each other in rows like 
shingles on a roof. These make a pretty picture as the pod in drying splits 
along the suture on the convex side, and exposes them to view. The silky 

tnlt- of numerous long, delicate- white hairs on the inner end of each seed, 

in drying, bristle out, and thus lilt the seeds out of their enclosure, where 
they arc lilted like fairy balloons, buoyenl a^> vapor, they go bearing the 
precious burden of an embryo plant, which Is to take its place as a contest- 
ant in the luii le i' >r existence. 

680. The virgin's bower. The virgin's bower (Clematis virginiana), too. 
clambering over fence and -luck, make! a shoi* of having transformed its 



SEED 1) IS 7 'RIB C 7VO.Y. 



373 



exquisite white flower clusters into grayish-white puffs, which scatter in the 
autumn gusts into hundreds of arrow-headed, spiral plumes. The achenes 




Fig. 475- 
Seed distribution of virgin's bower (clematis). 

have plumose styles, and the spiral form of the plume ^ives a curious twist 
to the falling seed (fig. 474). 



CHAPTER LIL 

STRUGGLE FOR OCCUPATION OF LAND. 

681. Retention of made soil. — In the struggle of plants for 
existence, there are a number of species which stand ready to 
rush in where new opportunities present themselves by changed 
conditions, or by newly made soil. The permanent drainage of 
ponds or marshes brings changed conditions, and the flora there 




Fig. 476. 
Made soil at mouth of stream, being overgrown by plants. Ithaca, N. Y. 

undergoes remarkable transformations. The deposits of the 
washings of streams in protected places along the shores, or at 
their mouths, where deltas or lateral plateaus are made by the 
accumulations of soil scoured off the banks of the stream, or 
washed off the fields during rains, make new ground. With such 
banks of newly made ground are deposited seeds carried along 
with the soil, or dropped there by the wind, by birds, or other 
agencies of seed distribution. 

682. Figure 476 is from a photograph taken at the mouth of 
one of the streams emptying into Cayuga Lake. At the left is 

374 



OCCUPA T10N OF LAND. 



375 




37^ ECOLOGY. 

a newly made bank of soil. The species of bidens were here 
among the first to start in the soft black mud. These are fol- 
lowed later by grasses, by species of the arrowhead (sagittaria), 
pickerel-weed (pontederia), etc. The loose soil becomes per- 
meated by a mass of roots, and year by year becomes more firm. 

683. Vegetation of sand dunes. — Along the sandy beaches 
of lakes, or of the ocean, drift piles of the fine sand are formed, 
which often are moved onward by the wind. The surface parti- 
cles are moved onward to the leeward of the drift, and so on. 
The form and location of the sand dune gradually changes. 
Such drifts sometimes slowly but surely march along over soil 
where a rich vegetation grows, and over valuable land. Even 
on these sand dunes there are certain plants which can gain a 
foothold and grow. When a sufficient number obtain a foothold 
in such places they retain the sand and prevent the movement 
of the dune. 

684. Reforestation of lands. — When by the action of fire or 
wind, or through the agency of man, portions of forests are 
partially or completely destroyed, a new set of conditions is pre- 
sented over these areas. One of the most important is that light 
is admitted where before towering trees permitted but a limited 
and characteristic undergrowth to remain. Hundreds of forms, 
which for years have been dormant, are now awakened from 
their long sleep, and new and recent importations of seeds which 
are constantly rushing in spring into existence to fill the gap, 
multiply their numbers, and make more sure the perpetuation 
of their kind. 

685. The earliest to appear are not always the ones to endure 
the longest, and a battle royal takes place during years for su- 
premacy. The weaker ones are gradually overcome by the more 
vigorous, and a new crop of trees, which often springs up in such 
places, finally usurps again the domain, in the name of the same 
or of a different species. 

686. Domestic plants protected by man occupy cultivated 
fields. When cultivation ceases, or the crop is removed, or the 
fields are neglected, hundreds of species of feral plants, which 



OCCUPA TIOiV OF LAND. 



377 



are constantly springing up, now flourish, bear seed, and take 
more or less complete possession of the soil. Impoverished land, 
abandoned by man, becomes nurtured by nature. Weeds, grass, 
flowers, spring up in great variety often. Some can thrive but 
little better than the abandoned crops, while others, peculiarly 
fitted because of one or another adapted structure or habit, flour- 




Fig. 47s. 

Abandoned field, in Alabama, growing up to broom-sedge and trees. (Photograph by Prof. 
P. H. Mell.) 



ish. Crab-grass and other low-growing plants often cover and 
protect the soil from the direct rays of the sun, and thus conserve 
moisture. The clovers which spring up here and there, by the 
aid of the minute organisms in their roots, gather nitrogen. 
The melilotus, the passion flower, and other deep-rooted plants 
reach down to virgin soil and lift up plant food. Each year 
plant remains are added to, and enrich, the soil. In some places 
grasses, like the broom -sedge (andropogon) succeed the weeds, 
and a turf is formed. 

687. Seeds of trees in the mean time find lodgment. During 
the first few years of their growth they are protected by the 



378 



ECOLOGY. 



herbaceous annuals or perennials. In time they rise above 
these. Each year adds to their height and spread of limb, until 
eventually forest again stands where it was removed years before. 
In the Piedmont section of the Southern States such a view as is 







Fig. 479. 
Abandoned field, Alabama, sell reforested by pines (Photograph by Prof. 1*. H. Mell.) 

presented in fig. 478 represents how abandoned fields are taken 
by the broom-sedge, to be followed later by pines, and later 
by a forest as shown in fig. 479. 

688. In New York State many abandoned hillsides are being 
reforested slowly by nature with the white pine. Fig. 480 rep- 
resents a group of self-sown pines ranging from three to six 



OCCUPATION OF LAND. 



379 



meters high (10—20 feet), growing up in an abandoned orchard 
near Ithaca. In this reforestation of impoverished lands, man 
can give great assistance by timely and proper planting. 




Fig. 480. 

Seif-sown while pine in abandoned orchard ; trees 9-20 years old. Near Ithaca. (Photo- 
graph by the author.) 

689. Beauty of old fields. — During one season from my win- 
dow I beheld a marvellously beautiful sight. The scene was 
located in a portion of an old field on a hillside, in a rapidly 
growing part of the city. New buildings had sprung up all 



3 8o 



ECOLOG Y. 



around, and this was waiting sale or improvement. But there 
were innumerable seeds of a great variety of plants in that vacant 
lot. They sprang into growth to occupy the land, and a great 
tangle of luxuriant vegetation was the result. Burdock, tower- 
ing pigweeds, grasses, beggar-ticks, mullein, St. John's wort, 
masses of giant goldenrods, blue-rayed asters, occupied every 
inch of the ground in a grand medley of kind and color. 
Through this mass, briers and blackberry bushes pushed their 
thorny sprays, laying hold on you if you attempted entrance. 
Children plucked the beautiful flowers, but the flowers they 
cared not, neither took they thought for the future day when 
they must give way under the influence of man to stone walls 
and a plain greensward, so joyous were they in the mere 
thought of existence and radiant beauty. 



CHAPTER LIIL 

SOIL FORMATION IN ROCKY REGIONS AND 
IN MOORS. 

Lichens. 

690. Many of the lichens are small and inconspicuous. They 
often appear only as bits of color on tree trunk or rock. One 
of the conspicuous ones on stones lying on the ground is the 
grayish-green thallus of Parmelia contigua (fig. 481). Its pretty, 
flattened, forking lobes radiate in all directions, advancing at the 
margin, and covering year by year more and more of the stone 
surface. Numerous cup-shaped fruit bodies (apothecia) are scat- 
tered over the central area. The thallus clings closely to the rock 
surface by numerous holdfasts from the under side, which pene- 
trate minute crevices of the rock. The lichen derives its food 
from the air and water. By its closely fitting habit it retains in 
contact with the rock certain acids formed by the plant in 
growth, or in the decay of the older parts, which slowly disinte- 
grate the surface ot the rock. These disintegrated particles of 
the rock, mingled with the lichen debris, add to the soil in those 
localities. 

691. Lichens are among the pioneers in soil making. — 
The habit which many lichens have of flourishing on the bare 
rocks fits them to be among the pioneers in the formation of soil 
in rocky regions which have recently become bared of ice or 
snow. The retreat of glaciers from peaks long scoured by ice, 
or the unloading of broken rocks along its melting edge, exposes 
the rocks to the weathering action of the different elements. Now 
the lichens lay hold on them and invest them with fantastic 

381 



382 



ECOLOGY. 



figures of varied color. Disintegrating rock, debris of plants 
and animals, join to form the virgin soil. Certain of the blue- 
green algae, as well as some of the mosses, are able to gain a 
foothold on rocks and assist in this process of soil formation. 





Fig. 481. 
Rock lichen (Parmelia contigua). 

A view of rocks thrown down by the melting and retreating edge 
of a glacier in Greenland is shown in fig. 481. These rocks at 
the time the photograph was taken had no plant life on them. 
At other places in the vicinity of this glacier, rocks longer uncov- 
ered by ice were being covered by plant life. One of the green- 
land rock lichens are shown in fig. 483. 



SOIL FORMATION: ROCK DISINTEGRATION. 383 

692. Other plants of rocky regions. — Certain of the higher 
plants also find means of attachment to the bare rocks of the 
arctic and mountain regions. The roots penetrate into narrow 
crevices in the rock, and are able to draw on the water which is 




Fig. 482. 
Edge of glacier in Greenland, showing freshly deposited rocks. (From Prof. R. S. Tarr.) 



elevated by capillarity. Such plants, however, which live on 
bare rocks, whether in the arctic or in mountain regions, have 
leaves which enable them to endure long periods of drought. 
These plants have either succulent leaves like certain of the stone- 



384 



ECOLOGY. 



crops (sedum), or small thick leaves which are closely overlapped 
as in the Saxifraga oppositifolia. 

693. Few of us, unfortunately, can make the trip to the arctic 
regions to study these interesting plants which play such an im- 
portant role in the economy of nature. Rocky places, however, 




Fig- 4**3- 
Rock lichen (umbilicaria) from Greenland. 

or loose stones are common nearer home. Observation of their 
flora, and the means by which such plants derive nutriment, store 
moisture, or protect themselves from drought, will well repay out- 
door excursions. 

694. Filling of ponds by plants. — Not only arc plants im- 
portant agencies in the formation of soil in rocky regions, they 



SOIL FORMATION: MOORS. 



335 




386 ECOLOGY. 

are slowly but surely playing a part in the changes of soil and in 
the topography of certain regions. This is very well marked in 
the region of small ponds, where the bottom slopes gradually out 
to the deeper water in the center. Striking examples are some- 
times found where the surface of the country is very broken 
or hilly with shallow basins intervening. In what are termed 
morainic regions, the scene of the activity of ancient glaciers, 
or in the mountainous districts, we have opportunities for study- 
ing plant formations, which slowly, to be sure, but nevertheless 
certainly, fill in partly or completely these basins, so that the 
water is confined to narrow limits, or is entirely replaced by plant 
remains in various stages of disintegration, upon which a charac- 
teristic flora appears. 

695. A plant atoll. — In the morainic regions of central New 
York there are some interesting and striking examples of the ef- 
fects of plants on the topography of small and shallow basins. 
These formations sometimes take the shape of "atolls," though 
plants, and not corals, are the chief agencies in their gradual ev- 
olution. Fig. 484 is from a photograph of one of these plant atolls 
about 15 miles from Ithaca, N. Y. , along the line of the E. C. & 
N. R. R. near a former flag station known as Chicago. The basin 
here shown is surrounded by three hills, and is formed by the 
union of their bases, thus forming a pond with no outlet. 

696. Topography of the atoll moor. — The entire basin was 
once a large pond, which has become nearly filled by the growth 
of a vegetation characteristic of such regions. Now only a small, 
nearly circular, central, pond remains, while entirely around the 
edge of the earlier basin is a ditch, in many places with from 
30-600//. of water. There is a broad zone of land then lying 
between the central pond and the marginal ditch. Just inside of 
the ring formed by the ditch is an elevated ring extending all 
around, which is higher than any other part of the atoll. On a 
portion of this ring grow certain grasses and carices. The soil for 
some depth shows a wet peat made up of decaying grasses, carices, 
and much peat moss (sphagnum). In some places one element 
seems to predominate, and in other cases another element. On 



SOIL FORMATION: MOORS. 387 

some portions of the outer ring are shrubs one to three meters in 
height, and occasionally small trees have gained a foothold. 

697. Next inside of this belt is a broad, level zone, with Carex 
filiformis, other carices, grasses, with a few dicotyledons. Inter- 
mingled are various mosses and much sphagnum. The soil for- 
mation underneath contains remains of carices, grasses, and 
sphagnum. This intermediate zone is not a homogeneous one. 
At certain places are extensive areas in which Carex filiformis 
predominates, while in another place another carex, or grasses 
predominate. 

698. A floating inner zone. — But the innermost zone, that 
which borders on the water, is in a large measure made up of the 
leather-leaf shrub, cassandra, and is quite homogeneous. The 
dense zone of this shrub gives the elevated appearance to the 
atoll immediately around the central pond, and the cassandra is 
nearly one meter in height, the " ground " being but little above 
the level of the water. As one approaches this zone, the ground 
yields, and by swinging up and down, waves pass over a consid- 
erable area. From this we know that underneath the mat of 
living and recent vegetation there is water, or very thin mud, so 
that a portion of this zone is " floating." 

699. The inner, or cassandra, zone is more unstable, that is 
it is all "afloat," though firmly anchored to the intermediate 
zone. The roots of the shrubs interlace throughout the zone, 
firmly anchoring all parts together, so that the wind cannot break 
it up. Between the tufts of the cassandra are often numerous 
open places, so that the water or thin mud on which the zone 
floats reaches the surface, and one must exercise care in walking 
to prevent a disagreeable plunge. No resistance is offered to a 
pole two to three meters long in thrusting it down these holes. 
Grasses, carices, mosses, sphagnum, and occasionally moor-loving 
dicotyledons occur, anchored for the most part about the roots 
of the cassandra. Standing at the inner margin of the cassandra 
zone, one can see the mud, resembling a black ooze, formed of 
the titrated plant remains, which have floated out from the bot- 
tom of the older formations. In some places this lies very near 



388 



ECOLOGY. 







SOIL FORMATION: MOORS. 389 

the surface, and then certain aquatic plants like bidens, and 
others, find a footing. Upon this black ooze the formation can 
continue to encroach upon the central pond. Agitated by the 
wind, more and more of the ooze passes outward, so that in time 
there is a likelihood that the pond will cease to exist, yielding, 
as it has in other places, the right of possession to the conten- 
tious vegetation. 

700. How was the atoll formed? — In the early formation of 
the atoll, it is possible that certain of the water-loving carices and 
grasses began to grow some distance (three to four meters) from 
the shore, where the water was of a depth suited to their habit. 
The stools of these plants gradually came nearer the surface of 
the water. As they approach the surface, other plants, not so 
strong-rooted, like mosses, sphagnum, etc., find anchorage, and 
are also protected to some extent from the direct rays of sunlight. 
Partial disintegration of the dead plant parts and mingling with 
the soil gradually fills on the inside of the zone, so that the depth 
of the water there becomes less. Now the zone of the carices 
can be extended inward. 

701. The continued growth of the sphagnum and the dying 
away of the lower part of the plant add to the bulk of the plant 
remains in the zone, and finally quite a firm ground is formed, 
shutting off the shallow water near the shore from the deeper 
water of the pond. As time goes on other plants enter and 
complicate the formation, and even make new ones, as when the 
cassandra takes possession. 

702. The original pond here was rather oblong, and one end 
possibly much shallower than the other, so that it filled in much 
more rapidly, leaving the central pond at the east end. Over 
a portion of the west end there is an extensive cassandra forma- 
tion, w T ith some ledum (labrador tea), but separated from the 
circular cassandra zone by an intermediate zone. In this end- 
cassandra formation other shrubs, and white pines five to fifteen 
years old, are gaining a foothold, and in a quarter of a century 
or more, if left undisturbed, one may expect considerable changes 
in the flora of this atoll. It is possible that a rise of the water 



390 



ECOLOGY. 







for a number of 
years when the 
earlier zones were 
floating accounts 
for the circular ele- 
vation and atoll 
formation. 

703. A black- 
spruce moor. — A 
somewhat similar 
but more advanced 
plant formation oc- 
curs east of Free- 
ville, N. Y., and 
about nine miles 
distant from Ithaca. 
The center of the 
basin, which was 
perhaps shallower 
than the former 
one, has become 
completely filled, 
and all of the cen- 
tral formation is 
more elevated than 
the margin by the 
shore of the basin. 
All around the mar- 
gin in wet weather 
the ground is more 
or less submerged, 
while all the central 
portion is so ele- 
vated that the nu- 
merous stools or 
h u m mocks of 



SOIL FORMATION ': MOORS. 39 1 

grasses uke eriophorum, with its white tufts sparkling in the 
sunlight like a firmament of stars, shrubs like cassandra, pyrus, 
nemopanthes, etc., support one in walking above the water which 
rises in the intervening spaces. Sphagnum, polytrichum, and 
other mosses grow, especially in the stools of the other plants, 
where they now are shaded by the larger growth, and in drier 
seasons catch the water which trickles down during rain. 

Years ago the forest encroached on this formation, and trees of 
the hemlock-spruce, black spruce, larch, etc., of considerable size 
gained a footing, first along the margin, then along the more ele- 
vated zone a short distance within. The black spruce trees spread 
all over the center of the formation, attaining a height of one to 
six or eight meters, while the trees of the marginal zone where they 
first entered, and the ground is somewhat more elevated, attained 
a much greater height. 

704. Fall of the trees on the marginal zone when the wind 
break was removed. — These large trees of the marginal zone, 
though they were rooted to a great extent in loose soil, never- 
theless were protected from winds by the forests on the sur- 
rounding hills. When, however, these hills on three sides were 
cleared for cultivation the wind had full sweep, and many of 
the large trees were uprooted by the force of the gales. This 
view is supported by the fact that the western hill is still covered 
by forest, and large spruce trees of the marginal zone are still 
standing, though several were uprooted September, 1896, during 
a fierce southeastern gale, the wind from this direction having 
full play upon them. 

705. Dying of the spruce of the central area. — This re- 
moval of the forests from the surrounding hills very likely had 
its influence in hastening the melting of the winter snows on the 
hills, so that excessive quantities of water from this source rushed 
quickly down into the swamp, flooding it at certain seasons 
much higher than the normal high-water mark during former 
times, when the hills were forest-covered. Also during rains 
the water would now rush quickly down into the swamp, flood- 
ing it at these times. This greater quantity of water has had its 



392 



ECOLOG Y. 



effect, probably, in causing many of the young spruces over the 
center of the formation to die off. 

706. This may also have been hastened by fires which would 
now more often sweep over the swamp during dry seasons. In 
partial evidence of this are many young spruce trees with scars 
near the ground where the bark has been destroyed. This gives 
admittance to wood-boring insects which farther aid in the proc- 




Fig. 487. 
Dying black spruce in moor. (Photograph by the author.) 



I 



css of weakening and debilitating the trees. The dying off of 
the lower limbs of these marsh spruces suggests both the action 
of fire, as well as excessive moisture at times. Many of them 
now present only a small convex top of living branches. It is 
interesting to observe the gradation in this respect in different 
trees. 

707. The weird aspect presented by a clump of these dying 
young spruce trees is heightened also by the changes in the form 
of the branches as they die. The living branches have a graceful 
sigmoid sweep with their free ends curving upwards as in many 



SOIL FORMATION : MOORS. 393 

conifers. As the branches die, the free ends curve downward 
more and more, all gradations being presented in a single tree. 
A group of such dying spruce trees is shown in fig. 487. Some 
have been long dead ; only the knotted, weather-beaten trunks 
still remain tottering to their final condition. Others with leaf- 
less, dried, sprawling branches go swirling with every wind, 
while a few struggle on in the presence of these untoward con- 
ditions. 

708. Other morainic moors. — In other basins, where the 
hills on all sides are still forest-clad, more equable temperature 
and moisture conditions are conserved. This permits plants to 
flourish here which in the exposed basins are disappearing from 
the formations or only leading a miserable existence. This is 
strikingly true of some sphagnum formations. In the atoll for- 
mation described the evidence suggests that sphagnum formerly 
played a more active part in the evolution of that type of moor 
than has been the case since the hills were denuded of their 
trees. So also in the spruce moor, sphagnum probably was at 
one time a prominent factor in the formation of the early vege- 
tation. But excessive drought during certain seasons, and full 
exposure to the sun and wind, have served to lessen its influence 
and importance. But where protected from the wind, to a large 
extent from the heat of the sun, and supplied with a suitable 
moisture condition, the sphagnum flourishes. It grows either 
alone in shallow water, encroaching more and more on the center 
of the basin, or follows after and anchors among water-loving 
grasses and carices. In some cases it may thus largely cover 
such earlier formations. An examination of the sphagnum 
plant shows us how well it is adapted to flourish under such 
conditions. The main axis of the plant bears lateral branches 
nearly at right angles, but with a graceful downward sweep at 
the extremity. These primary lateral branches bear secondary 
branches, which arise, usually several, from near the point of 
attachment to the main axis. They hang downward, overlap on 
those below, and completely cover the main axis or stem. The 
leaves of sphagnum are peculiarly adapted for the purpose of 



394 



ECOLOG Y. 



taking up quantities of water. Not all the cells of the leaf are 
green, but alternate rows of cells become broadened, lose their 

chlorophyll, and their protoplasm 
collapses on the inner faces of the 
cell walls in such a way as to form 
thickened lines, giving a peculiar 
sculpturing effect to them. Perfora- 
tions also take place in the walls. 
These empty cells absorb large quan- 
tities of water, and by capillarity it 
is lifted on from one cell to another. 
These pendent branches, then, which 
envelop the sphagnum stem, lift 
water up from the moist substratum 
to supply the leaves and growing 
parts of the plant which are at the 
upper extremity. 

709. Year by year the extension 
of the sphagnum increases slowly 
upward by growth of the ends of 
the individual plants, while the older 
portions below die off, partly disin- 
tegrate, and pass over into the in- 
creasing solidity and bulk of the 
peat. It thus happens sometimes 
that the centers of such basins or 
moors are more elevated than the 
margins, because here a greater 
amount of water exists in the depths 
which is pumped up for use by the 
plants themselves. Such a formation 
is sometimes called a " high moor." 
710. Because of the peculiar topographic features of these 
basins, together with the conditions of moisture, etc., changes 
in their form are quite readily observed. But no less important 
are the influences of plants on soil conditions on the hills, and 




Fig. 488. 
Two fruiting plants of sphagnum 
( From Kerner and Oliver.) 



SOIL FORMATION: MOORS. 



395 



in more level areas. Old plant parts, and plant remains, by 
decay add to the bulk, fertility, and changing texture and phy- 
sical condition of the soil. 




Fig. 489. 
Where isoetes grows. A sa.ali morainic basin near Ithaca. (Photograph by the author.) 

711. The bald cypress (Taxodium distichum). — Very char- 
acteristic are the formations presented by the forests of the bald 
cypress of the South, which grows in swampy or marshy places. 
The " knees " on the roots of this cypress make grotesque figures 
in the cypress forest. These take the form of upright, columnar 
outgrowths, broader at the base or point of attachment to the 



396 



ECO LOG Y. 



horizontal root, and possess a fancied resemblance to a knee. 
These knees are said to occur at points on the horizontal root 
above and opposite the point where a root branch extends down- 
ward into the soft marsh soil. They thus give strength to the 










\ \„ ,- - 


1 


T.' •• ' . 


pi 


M82J 


r \ M 
Ml 












j^^^B 














IwaP^ ^g^ 










"j^tPR 



Fig. 490. 
Cypress knees, Mississippi. (Photograph by H. von Schrenk.) 

horizontal root at the point of attachment of the branch which 
penetrates into the soft soil, and during gales they hold these 
root branches more rigidly in position than would be the case if 
the horizontal root could easily bend at this point. The knees 
thus are supposed by some to strengthen the anchor formed by 
the root in the loose soil. Their development may be the result 
of mechanical irritation at these points on the horizontal root, 



SOIL FORMATION: MOORS. 397 

brought about by the strain on the roots from the swaying of the 
tree. Others regard them as organs for aerating the portions of 
the root system which are usually submerged in water or wet 
soil. The knees catch and hold floating plant remains during 
floods, and by the decay of this debris the fertility of the soil is 
increased. In deeper water where the lower part of the tree is 
constantly submerged, peculiar buttresses are sometimes formed 
on the trunk, as shown in figure 491. 



393 



ECOLOG v. 




SOU FORMATION: MOORS. 



399 




CHAPTER LIV. 

ZONAL DISTRIBUTION OF PLANTS. 










712. On the margins of lakes or ponds, where the slope is 
gradual from the land into the water, one often has an oppor- 
tunity to study the relation 
of various plants to different 
conditions of soil and water. 
In rowing near the south shore 
of Lake Cayuga, I have often 
been impressed with the defi- 
nite areas occupied by certain 
plants. Figure 492 is from a 
photograph, taken from the 
boat, of the shore distribution 
of these plants. The most 
striking feature here is the 
grouping of certain kinds of 
plants in definite lines or 
zones. Here the limitations 
of the zones are quite distinct, 
so that the transition from 
one zone to another is quite 
abrupt, though there is some 
mixture of the kinds at the 
zone of transition , or tension 
line. 

713. This arrangement of 
plants under such environ- 
ed// distribution 0/ plants. ' ' The 

400 



. 




Fig- 493- 
Sagittaria variabilis. 

mental influences is termed 



ZONAL DISTRIBUTION OF PLANTS. 



401 



slope where this photograph was taken is so symmetrical that 
plants suited by their long habit of growing at certain depths of 
water, or in soil of a certain moisture content, are readily drawn 




Fig. 494. 
Sagittaria variabilis. 

into zones parallel with the shore line. Several zones can be 
readily made out in this region; two of them at least do not show 
in the picture since they are submerged. 

714. If we treat of the two submerged zones, the first one is 
in the rear of the point from where the photograph was taken, 
and consists of extensive areas of chara in four to five meters of 



402 



ECOLOGY. 



water. The second zone then is in the water shown in the fore- 
ground of the picture. The plants here are also submerged, or 
only a small portion reaches the surface of the water, and so the 







Fig- 495- 
Sagittaria heterophylla. Often forms a zone just outside of the Sagittaria variabilis. 

zone does not show. In this zone occurs the curious Vallesneria 
spiralis, with its corkscrew flower stem, and various potamoge- 
tons. 

715. In the third zone, or the first one which shows in the 
picture, are great masses of the arrow-leaf (sagittaria) so variable 






ZONAL DISTRIBUTION OF PLANTS. 



403 



P i-rl 






* 




404 



ECOLOG Y. 







£ _1 



u 
B 



ZONAL DISTRIBUTION OF PLANTS. 



405 



in the form of its leaves. Next is the fourth zone, made up here 
chiefly of bullrushes (scirpus), and occasionally are clumps of the 
cattail flag (typha). Behind this is the fifth zone, only to be 
distinguished at this distance by the bright flower heads of the 
boneset (Eupatorium perforatum) and joepye-weed (Eupato- 




Fig. 498. 
Bank of joepye-weed, Eupatorium purpureum. (Photograph by author.) 

rium purpureum), and the blue vervain (Verbena hastata), which 
occurs on the land. Willows make a compact and distinct sixth 
zone, while at the right, shown in figure 496 taken alongside 
this view, the oaks on the hillside beyond form a seventh zone, 
and still farther back is a zone of white pines, making the 
eighth, 

716. On the banks of a stream emptying into this end of the 
lake, after pursuing its sinuous course through wooded flats, are 
living pictures, which present a wealth of beauty in color and 
harmony of association and environment, charming to behold 



406 



ECOLOGY. 



and delightful to study. At the entrance (figure 497) a broad 
sweep of typha margins a projecting arm of the land which affords 
a quiet nook for the repose of mats of green algae, of such sorts 




Fig. 499. 
Pontederia, showing leaves and flower spike. 



as spirogyra, oedogonium, cladophora, etc., floating on the placid 
water in the foreground. Slender stems of zizania rise like 
shooting stars among the flags, with scirpus crowding near, 
while masses of the flowers of the thoroughwort are sheltered by 






ZONAL DISTRIBUTION OF PLANTS. 



407 



overhanging willows. On the left, pond-weeds (Potamogeton 
natans) and the yellow w r ater lily, or spatter-dock (nuphar), 




Fig. 500. 
Yellow water lily on jutting arm in stream. (Photograph by the author.) 



float their leaves and flowers on the quiet water, while the small 
yellow flowers of the mud plantain (Heteranthera graminifolia) 
glitter in the sunlight. The arrow-leaf (Sagittaria heterophylla, 



408 ECQLOG V. 

and variabilis) stand to their necks in the water. The shore 
near by is lined with sedges. Beyond these on the banks 
are masses of the white and purple eupatorium, with a goodly 
sprinkling of the swamp milkweed, its blossoms ablaze with 
color, while a long bank of willows forms a background of satis- 
fying green. 

717. Rowing up the stream, one passes in review minor for- 
mations, which exhibit less regularity of distribution and fewer 
individuals of one species. Pontederia still lingers along neai 
the shore, nearly touching the feet of the purple eupatorium on 
the bank. The yellow water lily, in groups here and there, 
points out the shallows, or traces the jutting arms of the shore, 
which in the distance seem to intercept the course, and the 
wavelets on the water toss into fantastic figures the mirrored 
shrubs and trees. In the quiet nooks the sunlight blazes down 
upon umbels ot the blue cornel and the pendent fruit clusters 
of the trailing nightshade. Banks of goldenrod are massed on 
one hand, and here and there stand gorgeous clusters of the 
arrow-leaved polygonum and of the yellow touch-me-not, while 
every now and then the sickly, blighting form of the cuscuta 
holds its \ ictims in a crushing embrace. 

718. Successions of waves running along the sunny shore 
throw lights and shadows, which chase each other up the trunks 
of overhanging trees in the form of rings of sunlight and shade, 
and then throw a quivering, shimmering light over the foliage. 
Fallen trees Stretch their weather-beaten and bleached trunks 
Over the stream, and their mirrored ghosts dance in the waves at 
your approach, while the towering elms beyond, smothered in 
the foliage and embrace oi the poison ivy, add to the weird 
1 leant v of the s< cue. 



ZONAL DISTRIBUTION OF PLANTS. 



409 





1 «Tk *a hv * 






fit MHirn 




*^"i> 


*1 X JEM ■hHB 



Fig. 501. 
Elms in background covered by poison ivy. (Photograph by the authors 



CHAPTER LV. 

PLANT COMMUNITIES: SEASONAL CHANGES. 

719. One of the interesting subjects for observation in the 
study of the habits and haunts of plants is the relation of plants 
to each other in communities. In the topography of the moors, 
and of the land near and on the margins of bodies of water, we 
have seen how the adaptation of plants to certain moisture con- 
ditions of the soil, and to varying depths of the water, causes 
those of a like habit in this respect to be arranged in definite 
zones. Often there is a predominating specks in a given zone, 
while again there may be several occupying the same zone, more 
or less equally sharing the occupation. Many times one species 
is the dominant form, while several others exist by sufferance. 

720. Plants of widely different groups may exist in the 
same community. — So it is that plants of widely different rela- 
tionships have become adapted to grow under almost identical 
environmental conditions. The reed or grass growing in the 
water is often accompanied by floating mats of filamentous algae 
like spirogyra, zygnema ; or other species, as cedogonium, coleo- 
chaete, attach themselves to these higher lords of creation ; while 
desmids find a lodging place on their surface or entangled in the 
meshes of the other algae. Chara also is often an accompaniment 
in such plant communities, and water-loving mosses, liverworts, 
and fern-like plants as marsilia. Thus the widest range of plant 
life, from the simple diatom or monad to the complex flowering 
plant, may, by normal habit or adapted form, live side by side, 
each able to hold it> place in the community. 

721. In field or forest, along glade or glen, on mountain 
slope or in desert regions, similar relationships of plants in 

410 

. 



PLANT COMMUNITIES : SEASONAL CHANGES. 4 1 1 



communities are manifest. r I ne seasons, too, seem to vegetate, 
blossom, and fruit, for in the same locality there is a succession 
of different forms, the later ones coming on as the earlier ones 
disappear. 

722. Seasonal succession in plant communities. — The 
wooded slopes in springtime teem with trill ium, dentaria, pod- 
ophyllum, and other vernal blossoms, while on the steeper hill- 
sides the early saxifrage is to be found. In the rocky portions 




Fig. 502. 
Azalea (Rhododendron nudicaulis). 

of the glen, which is also a favorite lodgment for this pretty, 
white saxifrage, the wild columbine loves to linger and dangle 
its spurred flowers. The lichen-colored ledge is wreathed with 
moss and fern. On the partly sunlit slopes the clusters of azalea 
are radiant with blossoms, while here and there the shad-bush, 
or service-berry (amelanchier), with its mass of white flower- 



412 



ECOLOG V. 




Fig. 503- 
Walking fern, climbing down a hillside. 



PLANT COMMUNITIES: SEASONAL CHANGES. 4 ! 3 

sprays, overhangs some cliff, and the cockspur thorn (Crataegus) 
vies with it in the profusion of floral display. Near by sheets of 
water pour themselves unceasingly on the rocks below, scattering 
spray on the thirsty marchantia. Out from the steep slopes 
above rise the graceful sprays of yew (taxus), shaded by the 
towering hemlock spruces. The "walking-fern" here, holding 
fast above, climbs downward by long graceful strides. 

723. But the scene shifts, and while these flowers cast their 
beauty for the season, others put on their glory. The flowering 





& 
^ 




fk 


»*t* 


** 


4 

p ■ • 


JB* **- - al 


W k Jfijlfc 




*4T 




MMafif 




" 


- r 
m 


w 


i 


5- ^ifr 1 



Fig. 504. 
Spray of kalmia flowers. 

dogwood spreads its deceptive bracts as a halo around the clus- 
ters of insignificant flowers. The laurel (kalmia) with its clus- 
ters of fluted pinkish blossoms is a joy only too brief. Smaller 
and less pretentious ones abound, like the whortleberries, am- 
phicarpsea, bush-clover (lespedeza), sarsaparilla, and so on. 

724. In the autumn the glen is clothed with another robe of 
beauty. With the fall of the "sere and yellow leaf," golden- 



4H 



ECOLOGY. 



rod and aster still linger long in beauty and profusion. When 
the leaves have fallen the witch-hazel (hamamelis) begins to 




Fig. 5°5- 
Spray of witch-hazel (hamamelis) with flowers ; section of flower below. 

flower, and the snows begin to come before it has finished 
spreading its curled yellow petals. 

725. The landscape a changing panorama. — In our temper- 
ate regions the landscape is a changing panorama ; forest and 
field, clothed with a changing verdure, don and doff their foliage 
with a precision that suggests a self-regulating mechanism. 

In the glad new spring the mild warmth of the' sun stirs the 
dormant life to renewed activity. With the warming up of the 
soil, root absorption again begins, and myriads of tiny root hairs 
pump up \\ater\' solutions of nutriment and various salts. These 
are carried to the now swelling buds where formative processes 
and growth elongate the shoot and expand the leaf. buds long 
wrapped in winter sleep toss back the protecting scales. In a 
multitude of ways the different shrubs and trees now discard the 
winter armature which has served so good a purpose, and tiny 
bud leaves show a multitude of variations from simple bud scale 
to perfect leaf, a remarkable diversification in which the plant 

from lateral members ol the Stem forms organs to ser\e such a 

variety of purpose under such diametrically opposed environ- 
mental conditions. 



PLANT COMMUNITIES: SEASONAL CHANGES. 4 I 5 



726. Refoliation of bare forests in spring. — There is a cer- 
tain charm watching the refoliation of the bare forests, when the 
cool gray and brown tints are slowly succeeded by the light yel- 
low-green of the young leaves, which presents to us a warming 




Fig. 506. 
Opening buds of hickory. 

glow of color. Then the snow-clad fields change to gray, and 
soon are enveloped in a living sea of color. The quiet hum of 
myriads of opening buds and flowers in harmony with the 
general awakening of nature, and the trickling streamlets which 
unite into the gurgling brooks, makes sweet music to our atten- 
tive minds. 



4i6 



ECOLOG V. 







727. The evergreens display a striking contrast of color. The 
leafy, fan-shaped branches of the hemlock-spruce (tsuga) are 




Fig. 507. 
Austrian pine, showing young growtli of branches in early spring. 

fringed with the light green of the new growth. The pines lift 
u}) numbers of cylindrical shoots, with the leaf fascicles for a 
time sheathed in the whitened scales, while the shoots are tipped 
with the brown or flame-colored female flowers, reminding one 



PLANT COMMUNITIES: SEASONAL CHANGES. 4*7 

of a Christmas tree lighted with numerous candles. The numer- 
ous clusters of staminate flowers suggest the bundles of toys and 
gifts, and one inquires if this beautiful aspect of some pines 
when putting on their new growth did not suggest the idea of 
the Christmas tree at yule time. 

728. The summer tints are more subdued. — As summer- 
time draws on the new needles of the pine are unsheathed, the 
light green tints of the forest are succeeded by darker and sub- 
dued colors, which better protect the living substance from the 
intense light and heat of midsummer. The physiological pro- 
cesses for which the leaf is fitted go on, and formative materials 
are evolved in the countless chlorophyll bodies and transported 
to growing regions, or stored for future use. In transpiration 
the leaf is the terminus of the great water current started by the 
roots. Here the nutrient materials, for which the water serves 
as a vehicle, are held back, while the surplus water evaporates 
into the air in volumes which surprise us when we know that it 
is unseen. 

729. Autumn colors. — As summer is succeeded by autumn, a 
series of automatic processes goes on in the plant which fits it 
for its long winter rest again. Long before the frosts appear, 
here and there the older leaves of certain shrubs lose more or 
less of the green color and take on livelier tints. With the dis- 
integration of the chlorophyll bodies, other colors, which in 
some cases were masked by the green, are uncovered. In other 
cases decomposition products result in the formation of new 
colors. These coloring substances to some extent absorb the 
sun's rays, so that much of the nitrogenous substances in the leaf 
may not be destroyed, but may pass slowly back into the stem 
and be stored for future use. 

730. Fall of the leaf. — The gorgeous display of color, then, 
which the leaves of many trees and shrubs put on is one of the 
many useful adaptations of plants. While this is going on in 
deciduous trees, the petiole of the leaf near its point of attachment 
to the stem is preparing to cut loose from the latter by forming 
what is called a separative layer of tissue. At this point the cells 



41 8 ECOLOGY. 

in a ring around the central vascular bundle grow rapidly so as to 
unduly strain the central tissue and epidermis, making it brit- 
tle. In this condition a light puff of wind whirls them away in 
eddies to the ground. The frosts of autumn assist in the separa- 
tion of the leaf from the stem, but play no part in the coloration 
of the leaf. 

As the cold weather of autumn and winter draws slowly on, 
these trees and shrubs cast off their leaves, and thus get rid of 
the extensive transpiration surface, or in same cases the dead 
leaves may cling for quite a long period to the trees. However 
in the death and fall of the leaves of these deciduous trees and 
shrubs, or the dying back of the aerial shoots of perennial 
herbaceous plants, there is a most useful adaptation of the plant 
to lay aside, for the cold period, its extensive transpiration sur- 
face. For while the soil is too cool for root absorption, should 
transpiration go on rapidly, as would happen if the leaf surface 
remained in a condition for evaporation, the plants would lose 
all their water and dry up. 



CHAPTER LVI. 

ADAPTATION OF PLANTS TO CLIMATE. 

731. Some characteristics of desert vegetation. — One of the 

important factors in plant form and distribution is that of climate, 
which is modified by varying conditions, as temperature, hu- 
midity of the air, dryness, etc. In desert regions where the air 
and soil are very dry, and plants are subject to long periods of 
drought, there is a very characteristic vegetation, and a variety of 
forms have become adapted to resist the drying action of the 
climate. 

732. Some of the plants, especially the larger ones, have very 
succulent stems or trunks, or they are more or less expanded but 
thickened, while the leaves are reduced to mere spines or hairs, 
as in the cacti. If plants in desert regions had thin and broadly 
expanded leaves, transpiration would be so rapid, and so great, 
as to kill them. In these succulent stems there is a proportion- 
ately small surface area exposed, so that transpiration is reduced. 
The chlorophyll resides here in the stems, and they function as 
foliage leaves in many other plants do. 

733. Other plants of the desert, which do not have succulent 
stems, are provided with closely appressed and small, thick, 
scale-like leaves. The leaves in many of these plants have an 
epidermis of several layers of cells, so that transpiration does not 
take place so rapidly. In addition to this the stomata are sunk 
in pits, or cavities, so that the guard cells are not so exposed to 
the drying action of currents of air at the surface. 

734. In still other cases the leaves and stems are covered with 
a dense felt of hairs which serves as a cushion to protect them 

419 






420 



EC0L0G Y. 







Fig 

Birch trees from Greenland, one third natural size. 



ADAPTATION TO CLIMATE. 421 

from the direct rays of the sun, and also from the fierce blasts of 
dry air which frequently sweep over these regions. The hairs 
are so close, and so interwoven, that the air caught in the inter- 
stices is not easily displaced, and the leaves are not then subject 
to the drying effects of the passing winds. 

735. Some plants of temperate regions possess characters 
of desert vegetation. — Even in temperate regions in localities 
where the climate is more equable, certain plants, strangely, are 
similarly modified, or provided with protecting armor. The 
common purslane (portulacca) is an example of a succulent 
plant, and we know how well it is able to resist periods of 
drought, even when cut free from the soil. With the oncoming 
of rains it revives, and starts new growth, while in wet weather 
cutting it free from its roots scarcely interferes with its growth. 

736. Similarly the common mullein (Verbascum thapsus), the 
leaves and stems of which are so densely covered with stellate 
hairs, is able to resist dry periods. One can see how efficient this 
panoply of trichomes is by immersing the leaves in water. It is 
very difficult to remove the air from the interstices of the inter- 
woven trichomes so as to wet the epidermis. 

737. Alpine plants with desert characteristics. — Alpine 
plants (those on high mountains), as well as arctic plants, are 
similarly modified, having usually either succulent stems and 
leaves, or small, thick and appressed leaves, or leaves covered 
with numerous hairs. Cassiope, occurring on mountain summits 
of the northeastern United States, and far northward, has numer- 
ous needle-shaped, closely imbricated leaves. The plants need 
the protection afforded them by these peculiarities in these alpine 
and arctic regions because of the dry air and winds, as well as 
because of the bright sunlight in these regions. Because of the 
bright sunlight in alpine and arctic regions many of the plants 
are noted for the brilliant colors of the flowers. 

738. Low stature of alpine plants a protection against wind 
and cold. — Another protection to plants from winds and from 
the cold in such regions is their low stature. Many of the her- 
baceous plants have very short stems, and the leaves lie close tq 



422 



ECOLOGY. 







Fig. 509. 
Willows from Greenland, o'j j third natural size. 



ADAPTATION TO CLIMATE. 423 

the soil, the plants and flowers sometimes half covered with the 
snow. The heat absorbed by the soil is thus imparted to the 
plant. Trees in such regions (if the elevation or latitude is not 
beyond the tree line) have very short and crooked stems, and 
sometimes are of great age when only a foot or more high, and 
the trunk is quite small. In figure 508 are shown some birch trees 
from Greenland, one third natural size, the entire tree being here 
shown. Similarly figure 509 represents some of the arctic wil- 
lows, one third natural size. 

739. Some plants of swamps and moors present characters of 
arctic or desert vegetation. — Many of the plants of our swamps 
and moors have the characters of arctic or of desert vegetation, 
i.e. small, thick leaves, or leaves with a stout epidermis. The 
labrador tea (Ledum latifolium), an inhabitant of cold moors or 
mountain woods, has thick, stout leaves with a hard epidermis 
on the upper side, and the lower side of the leaves is densely 
covered with brown, woolly hairs. Transpiration is thus lessened. 
This is necessitated because of the cold soil and water of the 
moor surrounding the roots, which under these conditions absorb 
water slowly. Were the leaves broad with a thin and unpro- 
tected epidermis, transpiration would be in excess of absorption, 
and the leaves would wither. Cassandra, or leather-leaf, and 
chiogenes, or creeping snowberry, are other examples of these 
shrubs growing in cold moors. 

740. Hairs on young leaves protect against cold and wet. — 
Hairs on young leaves in winter buds afford protection from cold 
and from the wet. The young leaves of the winter buds of many of 
our ferns are covered with a dense felt of woolly hairs. In species 
of osmunda this is very striking. The leaves are quite well 
formed, though small, during the autumn, and the sporangia are 
nearly mature. The hairs are so numerous, and so closely mat- 
ted together, that they can be torn off in the form of a thick 
woolly cap. 



APPENDIX. 

COLLECTION AND PRESERVATION OF MATERIAL. 

Spirogyra may be collected in pools where the water is pres- 
ent for a large part of the year, or on the margins of large 
bodies of water. To keep fresh, a small quantity should be 
placed in a large open vessel with water in a cool place fairly 
well lighted. In such places it may be kept several months in 
good condition. 

Mucor may be obtained by placing old bread, etc., or horse 
dung, in a moist covered vessel. In the course of a week there 
should be an abundance of the mycelium and gonidia. From 
this material cultures may be made, if desired, in nutrient gela- 
tin or nutrient agar. 

Saprolegnia, or water mould, can be used for a study of pro- 
toplasm. Collect several dead house flies from window sills of 
neglected rooms. Immerse them in alcohol, then rinse in 
water to remove the alcohol. Then throw them in vessels of 
water containing freshly collected algae from several different 
places. In the course of a week there should be a tuft of whit- 
ish threads of the water mould surrounding the fly. 

Nitella is obtained in rather deep pools or ponds, or in slow- 
running water, at a depth of one to three feet usually. 

Stamen hairs or tradescantia can usually be obtained in 
greenhouses from flower buds just ready to open or just after 
opening. 

(Edogonium is often found in floating mats in ponds, or on 
the margins of slow-running streams, or of lakes. Frequently 
it is attached to other aquatic plants. Fruiting plants can be 

425 



426 APPENDIX. 

detected by certain of the cells being rounded and broader than 
others, and some of them at least usually containing the spores, 
a single spore nearly or quite filling the large cell, or oogonium. 
When it cannot be studied fresh it may be preserved in 2$ 
formalin or in 70^ alcohol, first placing it successively in 25$ 
and 50$ alcohol for a few hours. 

Some species of vaucheria occur in places frequented by 
cedogonium or spirogyra, while others occur in running water, 
or still others on damp ground. Frequently fine specimens of 
vaucheria in fruit may be found during the winter growing on 
the soil of pots in greenhouses. The jack-in-the-pulpit, also 
known as Indian turnip, growing in damp ground I have found 
when potted and grown in the conservatory yields an abundance 
of the vaucheria, probably the spores of the alga having been 
transferred with the soil on the plants. When material cannot 
be obtained fresh for study, it may be preserved in advance in 
formalin or alcohol as described for cedogonium. 

Coleochsete scutata is not so common as the cedogonium, 
spirogyra, or vaucheria. But it may be sometimes found with 
the small circular green disks adhering to rushes, grasses, or 
other aquatic plants in large ponds or on the margins of lakes. 
When found it is well to make permanent mounts of material 
killed in formalin, either in glycerine or glycerine jelly. 

Wheat rust. — The cluster-cup stage may be collected in May 
or June on the leaves of the barberry. Some of the affected 
leaves may be dried between drying-papers. Other specimens 
should be preserved in 2^ formalin or in 70^ alcohol. If the 
cluster cup cannot be found on the barberry, other species may 
be preserved for study. 

The uredospore and teleutospore stages can usually be found 
abundantly on wheat and oats, especially on late-sown oats which 
ripen in autumn. The affected leaves and stems may be pre- 
served dry. 

The powdery mildews are common during summer and au- 
tumn on a variety of leaves of shrubs, herbs, and trees. They 
can be recognized by the mildewed spots, or by the numerous 



COLLECTION AND PRESERVATION OF MATERIAL. 4 2 7 

minute black specks on the surface of the leaf. The leaves 
should be preserved dry after drying under pressure. 



Liverworts. 

Marchantia. — The green thallus (gametophyte) of marchan- 
tia may be found at almost any season, of the year along shady 
banks washed by streams, or on the wet low shaded soil. Plants 
with the cups of gemmee are found throughout a large part of 
the year. They are sometimes found in greenhouses, especially 
where peat soil from marshy places is used in potting. In May 
and June male and female plants bear the gametophores and 
sexual organs. These can be preserved in 2^% formalin or in 
7o r r alcohol. If one wishes to preserve the material chiefly for 
the antheridia and archegonia a small part of the thallus may be 
preserved with the gametophores, or the gametophores alone. 

In July the sporogonia mature. When these have pushed out 
between the curtains underneath the ribs of the gametophore, 
they can be preserved for future study by placing a portion of 
the thallus bearing the gametophore in a tall vial with 2$ for- 
malin. Plants with the sporogonia mature, but not yet pushed 
from between the curtains on the under side, can be collected in 
a tin box which contains damp paper to keep the plants moist. 
Here the sporogonia will emerge, and by examining them day 
by day, when some of the sporogonia have emerged, these plants 
can be quickly transferred to the vials of formalin before the spo- 
rogonia have opened and lost their spores. In this condition the 
plant can be preserved for several years for study of the gross 
character of the sporogonia and the attachment to the gameto- 
phyte. From some of the other plants permanent mounts in 
glycerine jelly may be made of the spores and elaters. 

Riccia. — Riccia occurs on muddy, usually shaded ground. 
Some species float on the surface of the water. It may be pre- 
served in 2$ formalin or 70^ alcohol. 

Cephalozia, ptilidium, bazzania, jungermannia, frullania, and 
Other foliose liverworts may be found on decaying logs, on the 



428 APPENDIX. 

trunks of trees, in damp situations. They may be preserved in 
formalin or alcohol. Some of the material may also be dried 
under pressure. 

Mosses are easily found and preserved. Male and female 
plants for the study of the sexual organs should be preserved in 
formalin or alcohol. In all these studies whenever possible living 
material freshly collected should be used. 

Ferns. 

For the study of the general aspect of the fern plant, polypo- 
dium, aspidium, onoclea, or other ferns may be preserved dry 
after pressure in drying sheets. A portion of the stem with the 
leaves attached should be collected. These may be mounted on 
stiff cardboard for use. The sporangia and spores can also be 
studied from dried material, but for this purpose the ferns should 
be collected before the spores have been scattered, but soon after 
the sporangia are mature. But when greenhouses are near it is 
usually easy to obtain a few leaves of some fern when the sporangia 
are just mature but not yet open. To prevent them from opening 
and scattering the spores in the room before the class is ready to 
use them, immerse the leaves in water until ready to make the 
mounts ; or preserve them in a damp chamber where the air is 
saturated with moisture. 

For study of the prothallia of ferns, spores should be caught 
in paper bags by placing therein portions of leaves bearing ma- 
ture sporangia which have not yet opened. They should be 
kept in a rather dry but cool place for one or two months. 
Then the spores may be sown on well -drained peat soil in pots, 
and on bits of crockery strewn over the surface. Keep the pots 
in a glass-covered case where the air is moist and the light is 
not strong. If possible a gardener in a conservatory should be 
consulted, and usually they are very obliging in giving sugges- 
tions or even aid in growing the prothallia. 

Lycopodium, equisetum, selaginella, isoetes, and other pteri- 
dophytes desired may be preserved dry and in 70$ alcohol. 

Pines. — The ripe cones should be collected before the seeds 



COLLECTION- AND PRESERVATION OF MATERIAL. 4 2 9 

scatter, and be preserved dry. Other stages of the development 
of the female cones should be preserved either in 70$ alcohol or 
in 2\<J C formalin. The male cones should be collected a short 
time before the scattering of the pollen, and be preserved either 
in alcohol or formalin. 

Angiosperms. — In the study of the angiosperms, if it is de- 
sired to use trillium in the living state for the morphology of the 
flower before the usual time for the appearance of the flower in 
the spring, the root-stocks may be collected in the autumn, and 
be kept bedded in soil in a box where the plants will be sub- 
jected to conditions of cold, etc., similar to those under which 
the plants exist. The box can then be brought into a warm 
room during February or March, a few weeks before the plants 
are wanted, when they will appear and blossom. If this is 
not possible, the entire plant may be pressed and dried for the 
study of the general appearance and for the leaves, w T hile the 
flower may be preserved in 2^ formalin, of course preserving a 
considerable quantity. Other material for the study of the plant 
families of angiosperms may be preserved dry, and the flowers 
in formalin, if they cannot be collected during the season while 
the study is going on. 

Demonstrations. — Upon some of the more difficult subjects in 
any part of the course, especially those requiring sections of the 
material, demonstrations may be made by the teacher. The ex- 
tent to which this must be carried will depend on the student's 
ability to make free-hand sections of the simpler subjects, upon 
the time which the student has in which to prepare the material 
for study, and the desirability in each case of giving demostra- 
tions on the minuter anatomy, the structure of the sexual organs 
and other parts, in groups where the material should be killed 
and prepared according to some methods of precision, now used 
in modern botanical laboratories. The more difficult demonstra- 
tions of this kind should be made by the instructor, and such 
preparations once made properly can be preserved for future 
demonstrations. Some of them may be obtained from persons 
who prepare good slides, but in such cases fancy preparations of 



43° APPENDIX. 

curious structures should not be used, but slides illustrating the 
essential morphological and developmental features. Directions 
for the preparation of material in this way cannot be given, in 
this elementary book, for want of space. 

Method of taking notes, etc. — In connection with the prac- 
tical work the pupil should make careful drawings from the 
specimens ; in most cases good outline drawings, to show form, 
structure etc., are preferable, but sometimes shading can be 
used to good advantage. It is suggested that the upper 2/3 of 
a sheet be used for the drawings, which should be neatly made 
and lettered, and the lower part of the page be iised for the 
brief descriptions, or names of the parts. The fuller notes and 
descriptions of the plant, or process, or record of the experi- 
ment should be made on another sheet, using one, two, three, 
or more sheets where necessary. Notes and drawings should be 
made only on one side of the sheet. The note-sheets and the 
drawing-sheets for a single study, as a single experiment, should 
be given the same number, so that they can be bound together 
in the cover in consecutive order. Each experiment may be 
thus numbered, and all the experiments on one subject then 
can be bound in one cover for inspection by the instructor. 
For example, under protoplasm, spirogyra may be No. 1, mucor 
No. 2, and so on. In connection with the practical work the 
book can be used by the student as a reference book ; and dur- 
ing study hours the book can be read with the object of arrang- 
ing and fixing the subject in the mind, in a logical order. 

The instructor should see that each student follows some well- 
planned order in the recording of the experiments, taking notes, 
and making illustrations. Even though a book be at hand for 
the student to refer to, giving more or less general or specific 
directions for carrying on the work, it is a good plan for every 
teacher to give at the beginning of the period of laboratory 
work a short talk on the subject for investigation, giving general 
directions. Even then it will be necessary to give each indi- 
vidual help in the use of instruments, and in making prepara- 
tions for study, until the work has proceeded for some time, 



APPARATUS AND GLASSWARE. 431 

when more general directions usually answer. The author does 
not believe it a good plan for the student to have written, 
minute, directions for preparing the plants and experiments. 
General directions and specific help where there is difficulty, 
until the student learns to become somewhat independent, seems 
to be a better plan. 



APPARATUS AND GLASSWARE. 

The necessary apparatus should be carefully planned and be 
provided for in advance. The microscopes are the most expen- 
sive pieces of apparatus, and yet in recent years very good mi- 
croscopes may be obtained at reasonable rates, and they are 
necessary in any well-regulated laboratory, even in elementary 
work. 

Microscopes. The number of compound microscopes will 
depend on the number of students in the class, and also on the 
number of sections into which the class can be conveniently 
divided. In a class of 60 beginning students I have made two 
sections, about 30 in each section ; and 2 students work with 
one microscope. In this way 15 microscopes answer for the 
class of 60 students. It is possible, though not so desirable, to 
work a larger number of students at one microscope. Some can 
be studying the gross characters of the plant, setting up appa- 
ratus, making notes and illustrations, etc., while another is en- 
gaged at the microscope with his observations. 

The writer does not wish to express a preference for any pat- 
tern of microscope. It is desirable, however, to add a little to 
the price of a microscope and obtain a convenient working 
outfit. For example, a fairly good stand, two objectives (2/3 
and 1/6), one or two oculars, a fine adjustment, and a coarse 
adjustment by rack and pinion, and finally a revolver, or nose- 
piece, for the two objectives, so that both can be kept on the 
microscope in readiness for use without the trouble of removing 
one and putting on another. Such a microscope, which I have 



43 2 APPENDIX. 

found to be excellent, is Bausch & Lomb's AAB (which they 
recommend for high schools), costing about $25.00 to $28.00. 
I have compared it with some foreign patterns, and the cost of 
these is no less, duty free, for an equivalent outfit. Of course, 
one can obtain a microscope for $18.00 to $20.00 without some 
of these accessories, but I believe it is better to have fewer 
microscopes with these accessories than more without them. 
Of the foreign patterns the Leitz (furnished by Wm. Krafft, 
411 W. 59th St., N. Y. ) and the Reichert are good, while Queen 
& Co., Philadelphia, Pa., and Bausch & Lomb, Rochester, 
N. Y., furnish good American instruments. 

Glass slips, 3X1 inch ; and circle glass covers, thin, 3/4 in. 
diameter. 

Glass tubing of several different sizes, especially some about 
^mm inside diameter and 7mm outside measurement, for root- 
pressure experiments. 

Rubber tubing to fit the glass tubing, and small copper wire 
to tighten the joints. 

Watch glasses, the Syracuse pattern (Bausch & Lomb), are 
convenient. 

U tubes, some about 20mm diameter and 10-15C7// long. 
Corks to fit. 

Small glass pipettes ("medicine droppers") with rubber 
bulbs. 

Wide-mouth bottles with corks to fit. Reagent bottles. (Small 
ordinary bottles about 10cm X 4cm with cork stoppers will an- 
swer for the ordinary reagents. The corks can be perforated 
and a pipette be kept in place in each ready for use. Such 
bottles should not be used for Strong acids.) 

Small vials with corks for keeping the smaller preparations in. 

Small glass beakers or tumblers. 

A few crockery jars for water cultures. 

Fruit jars for storing quantities of plant material. 
Glass graduates; 1 graduated to iooocc, 1 graduated to 
1 oocc. 

Funnels, small and medium (6 and loctn in width), 'lest 



APPARATUS AND GLASSWARE. 433 

tubes. A few petrie dishes. Bell jars, a few tall ones and a 
few low and broad. Thistle tubes. Chemical thermometer. 

Balance for weighing. A small hand-scale furnished by Eimer 
& Amend, 205-211 3d Ave., N. Y., is fairly good ($2.00). 

For pot experiments, the " Harvard trip-scale," Fairbanks 
Scale Co. (about $6.00). 

Apparatus stand, small, several, with clamps for holding test 
tubes, U tubes, etc. 

Agate trays, very shallow, several centimeters long and wide. 
Agate pans, deep, for use as aquaria, etc., with glass to cover. 

Paraffin or wax, for sealing joints in setting up transpiration 
apparatus. 

Mercury, for restoration of turgidity, and for lifting power of 
transpiration. 

Sheet rubber, or prepared vessels for enclosing pots to prevent 
evaporation of water from surface during transpiration experi- 
ments. 

Litmus paper, blue, kept in a tightly stoppered bottle. Filter 
paper for use as absorbent paper. Lens paper (fine Japanese 
paper) for use in cleaning lenses ; benzine for first moistening 
the surface, and as an aid in cleaning. 

For materials for culture solution, see Chapter III. 

Reagents. 

Glycerine, alcohol of commercial (95^) strength, formalin or 
formalose of 40$ strength, chloral hydrate crystals, iodine crys- 
tals, eosin crystals, fuchsin crystals, potassium iodide, potassium 
hydrate, potash alum. It is convenient also to have on hand 
some ammonia, sulphuric acid, nitric acid, and muriatic acid in 
small quantity. 

REAGENTS READY FOR USE AND FOR STORING PLANT MATERIAL 

IN. 

Alcohol. Besides the 95^ strength, strengths of 30^, 50$, and 
70$, for killing material and bringing it up to 70$ for storage. 



434 



APPENDIX. 



Formalin. Usually about a 2-|-^ is used for storing material, 
made by taking 97^- parts water in a graduate and filling in z\ 
parts of the 40^ formalin. 

Salt solution 5^ ; sugar solution 15$ (for osmosis). 
Iodine solution. Weak — to 300a: distilled water add 2 

grams iodide of potassium ; to 
this add 1 gram iodine crys- 
tals. 
Strong — use less water. 
Eosin. Alcoholic solution. Distilled water 50a;, alco- 
hol 50a;, eosin crystals \ gram, potash alum 4 
grams. 
Aqueous solution. Distilled water ioocc, eosin crystals 
1 gram. 
Chloral hydrate ; aqueous solution, nearly sat. sol. 
Schimper's solution. Chloral hydrate 5 parts, water 2 parts, 
iodine to make a strong color. 

Student list of apparatus. 

Several glass slips 3X1 inch, and more circle glass covers, 
thin and \ inch diameter. 

One scalpel. 

One pair forceps, fine points. 

Two dissecting needles (may be made by thrusting with aid of 
pincers a sewing needle in the end of a small soft pine stick). 

Lead-pencils, one medium and one hard. 

Note paper; a good paper, about octavo size, smooth, unruled, 
with two perforations on one side for binding. Several manila 
covers or folders to contain the paper, perforated also. Enough 
covers should be provided so that notes and illustrations on dif- 
ferent subjects can be kept separate. 



REFERENCE BOOKS. 

The following books are suggested as suitable ones to have on 
the reference shelves, largely for the use of the teacher, but sev- 



REFERENCE BOOKS. 435 

eral of them can with profit be consulted by the students also. 
There are a number of other useful reference books in Ger- 
man and French, and also a number of journals, which might be 
possessed by the more fortunate institutions, but which are too 
expensive for general use, and they are not listed here. 

Kerner and Oliver, Natural History of Plants. Blackie & Son, 
London, 1895. Henry Holt & Co., New York, 1895. 

Strasburger, Noll, Schenck & Schimper, A Text Book of Bot- 
any, translated by Porter. The Macmillan Co., New York, 
1S98. 

Vines, Student's Text Book of Botany. The Macmillan Co., 
New York, 1895. 

Atkinson, The Biology of Ferns. The Macmillan Co., New 
York, 1894. 

MacDougal, Experimental Plant Physiology. Henry Holt & 
Co., New York, 1895. 

Spalding, Introduction to Botany. D. C. Heath & Co., Bos- 
ton, 1895. 

Bessey, Essentials of Botany. Henry Holt & Co., New 
York. 

Goebel, Outlines of Classification and Special Morphology of 
Plants. Oxford, Clarenden Press, 1887. 

Warming & Potter, Hand Book of Systematic Botany. Mac- 
millan & Co., New York, 1895. 

DeBary, Comparative Morphology and Biology of the Fungi, 
Mycetozoa, and Bacteria. Oxford, Clarenden Press, 1887. 

Underwood, Our Native Ferns and their Allies. Henry Holt 
& Co., New York. 

Bailey, Lessons in Plants. Macmillan & Co,, New York, 
1898. 

Gray, Lessons and Manual of Botany. American Book Co., 
New York. 

Mliller, The Fertilization of Flowers. Macmillan & Co., New 
York. 

Darwin, Insectivorous Plants. D. Appleton & Co., New 
York. 



43^ APPENDIX. 

Darwin, The Power of Movement in Plants. D. Appleton & 
Co. , New York. 

Darwin, Cross and Self Fertilization in the Vegetable King- 
dom. D. Appleton & Co., New York. 

Warming, Oekologische Pflanzengeographie. Gebriider Born- 
trager, Berlin. 

Papers by Macmillan in the Bulletin of the Torrey Botanical 
Club and Minn. Bot. Studies, by Shaler in the 6th, 10th, and 
1 2th Annual Reports of the United States Geological Survey, 
and by Ganong in Trans. Roy. Soc. Canada, sec. ser. vol. 3, 
1897-98, should be consulted by those interested in ecology. 



Where materials cannot be readily collected in the region for 
class use, they can often be purchased of supply companies. 

The Cambridge Botanical Supply Co., Cambridge, Mass., 
supplies plant material of several groups for study, as well as 
apparatus and paper. 

The Ithaca Botanical Supply Co., Ithaca, N. Y., will supply 
plants for study in various groups, and upon order will prepare 
permanent slides for demonstration of the more difficult topics, 
such as the structure of the sexual organs of liverworts, mosses, 
ferns, etc. 



INDEX. 



Absorption, 13 

Aceraceae (A-cer-a ce-ae), 273, 
275, 298 

Acer saccharinum (A'cer sac- 
cha-ri'num), 275 

Adder tongue, formation of 
flower, 349 

Adiantum (A-di-an'tum), 169, 173 

Adiantum concinnum, spermato- 
zoids of, 181; embryo, 184, 185 

Adiantum cuneatum, fertiliza- 
tion, 182; embryo, 186 

vEcidiospore (y£-cid'i-o-spore), 

131 
yEcidium (^-cid'i-um), 132 
yEsculinae (y£s-cu-lin'ae), 273, 297 
Agaricus campestris (A-gar'i- 

cus cam-pes'tris), 136, 326-331 
Agaricus melleus, 338 
Aggregate, 290, 299 
Alga, Algae, 2 
Alismaceae (A-lis-ma'ce-ae), 254, 

255 
Alisma plantago, 254 
Amanita phalloides (Am-a-ni'ta 

phal-loi'des), 334, 335 
Almond (family), 276 
Amygdalaceae (A-myg-da-la'- 

ce-ae), 276, 295, 298 
Anemophilous, 353 
Angiosperms, comparative table 

of, 238 
Angiosperms, morphology of, 

221-236 
Antheridiophores, 145 
Antheridium, of vaucheria, 107; 

cedogonium, 101, 102; coleo- 

chaete, 112; saprolegnia, 123; 

erysiphe, 138; liverworts, 141, 

145, 146; mosses, 160, 161; 

ferns, 180, 181; selaginella, 

194; isoetes, 198 
Antipodal cells, 231, 233 
Apogamy, 245 



Apogeotropic (Ap-o-ge-ot'ro- 
pic), 83 

Apogeotropism (Ap-o-ge-ot'ro- 
pism), 83 

Apospory, 245 

Apple, 276 

Araceae (A-ra'ce-ae), 257, 294, 296 

Archegonia (Ar-che-go'ni-a) of 
liverworts, 141, 142, 155, 156; 
mosses, 160, 161; ferns, 176, 
181, 182; selaginella, 195; iso- 
etes, 198; gymnosperms,2io,2ii 

Archegoniophore, 147 

Archesporium (Ar-che-spor'i- 
um), 153, 239 

Arisaema triphyllum (Ar-i-sae'ma 
tri-phyl'lum), 257; germination 
of, and embryo, 311, 313; pol- 
lenation of, 360, 361 

Asclepias cornuti (As-clep'i-as 
cor-nu'ti), dissemination of 
seed, 372 

Ascomycetes (As-co-my-ce'tes), 
138, 139 

Ascospore, 137-139 

Ascus (pi. Asci), 137-139 

Ash (American), 304 

Aspidium acrostichoides, 165, 
172, 177 

Aspidium spinulosum, 168 

Asplenium bulbiferum, 174, 175, 

239 
Aster novae-angliae, 290, 291 
Atoll, made by plants, 386 
Azalea, 411 

Bacteria, nutrition of, 321 
Bald cypress, 395, 396 
Basidiomycetes (Ba-sid-i-o-my- 

ce'tes), 136, 139 
Bast, 44; fibres, 48; parenchyma, 

48 

Batrachospermum (Ba-tra-cho- 
sper'mum), 116 

437 



438 



INDEX. 



Bean, germination of, 307, 308 

Beet, osmose in, 15, 16, 17, 18 

Bell flower, 289 

Bicornes, 283, 284, 298 

Bidens, seed of, 368 

Bindweed, 284 

Black rust, 129 

Black spruce moor, 390 

Blasia, 155 

Bloodroot, 271 

Blue-green algae, 118 

Bluet, pollenation of, 354, 3^5 

Borage, 285 

Boraginaceae (Bor-ag-i-na'ce-ae), 

285, 299 
Buckwheat, 267 
Bur marigold, seeds of, 368 
Brown algae, 115, 118 
Bryony, tendril of, 88 
Butomus, 255 

Callithamnium, 119 

Caltha palustris, 268, 269 

Cambium, 44, 48 

Campanula, 289; pollenation of, 

362 
Campanulaceae, 289, 299 
Campanulinae, 289, 299 
Canna, pollenation of, 363-367 
Caprifoliaceae (Cap-ri-fo-li-a' 

ce-ae), 288, 296, 299 
Carbon conversion, 59, 61, 67, 68; 

rays of light concerned in, 67 
Carbon dioxide, absorption of, 

51; loss of, 54 
Carbon, food of plants, 59-64 
Carex laxiflora, 261 
Carex lupulina, 260 
Carnation rust, 323, 324 
Castor oil bean, germination of, 

308, 309 

Cattails, 257 

Cell, 3 

Cell sap, 3 

Cephalozia (Ceph-a-lo'zi-a), 155 

Chaetophora (Chae-toph'o-ra), 103 

Champia, 119 

Chlamydospores (Chlam-yd'o- 
spores), of mucor, 123 

Chlorophyceae (Chlo-ro-phy'ce- 
ae), 118 

Chlorophyll, 2. 65-69; band, 2; 
bodies, 66; movement of chlo- 
rophyll bodies, 68, 69 



Chloroplastid, 67 

Chloroplasts, 66, 68 ; starch 

formed in, 68 
Choke cherry, 276, 277 
Christmas fern, 165-167 
Chromatin, 240 
Chromatin skein, 241 
Chromoplasts, 68 
Chromosomes, 241-243 
Claytonia virginiana, 267 
Cleistogamous, 353, 354 
Clematis virginiana, 269, 270 ; 

dissemination of seed, 372, 373 
Closterium, 98 
Cosmarium, 98 
Club mosses, 191-195 
Cluster cup, 7.31, 132, 135 
Coleochaete (Co-le-o-chae te), 110- 

113 
Coleochaete scutata, no, 112 
Coleochaete soluta, 112 
Columella, of rhizopus, 121, 123 
Compositae, 290, 296, 299 
Conferva, 103 
Confervoideae (Con-fer-voi'de-ae), 

103, 118 
Conjugatae (Con-ju-ga'tae), 98, 118 
Conjugation, 94, 96 
Contortae, 287 
Convolvulaceae (Con-vol-vu-la' 

ce-ae), 284, 299 
Convolvulus (Con-vol'vu-lus), 

284, 285 
Cortex, 44 
Cruciferae (Cru-cif'er^ae), 272, 

295,297 
Cupuliferae (Cu-pu-lif'er-ae), 263, 

294, 296 
Curvembryae (Curv-em'bry-ae), 

268, 297 
Cuticularized, 37 
Cyanophyceae (Cy-an-o-phy'ce- 

ae), 118 
Cycas, 214-217 (see also frontis- 
piece.) 
Cyclosis (Cy-clo'sis), 9 
Cyperaceae (Cy-per-a'ce-ae), 259- 

261, 296 
Cypress knees, 396 
Cypripedium, 361, 365 
Cytisus (Cy-ti'sus), scattering of 

pollen, 363 
Cvstocarp, 116-119 
Cystopteris bulbifera, 174 



INDEX. 



439 



Cystopus candidus, haustoria of, 

'324 
Cytoplasm (Cy'to-plasm), 5 

Daucus carota, 281 

Dentaria, 221, 225, 227 

Desert vegetation, characters of, 

419 
Desmids, 98 

Desmodium (Des-mo'di-um), dis- 
semination of seeds, 368 
Diadelphous (Di-a-del'phous), 

272 
Diageotropism (Di-a-ge-ot'ro- 

pism), 83 
Diahelio tropic (Di-a-he-li-ot'ro- 

pic), S4, 86 
Diaheliotropism (Di-a-he-li-ot - 

ro-pism), 84, 86 
Dicentra canadensis (Di-cen'tra 

can-a-den'sis), 271 
Dichogamous (Di-chog'a-mous), 

360 
Dicotyledons, 262-293 
Diffusion, 13 
Dionaea muscipula (Di-o-nae'a 

mus-cip'u-la), 90 
Dipsacaceae (Dip-sa-ca'ce-ae), 

289, 296, 299 
Dipsacales (Dip-sa-ca'les),289,299 
Dodder, nutrition of, 321 
Dorsiventral, 88 
Downy mildews, 128 
Drosera (Dros'e-ra), 90 
Duck weeds, 314, 3T5 

Ecology (sometimes written (Ecol- 
ogy), 300-423 

Elaters, 150 

Embryo, of angiosperms, 232,235 

Embryo sac, 229-233 

Endosperm, 209-211, 234, 235 

Epidermal system, 48 

Epigynous, 255 

Epinastic (Ep-i-nas tic), 86 

Epinasty (Ep-i-nas'ty), 86 

Epipactis, pollenation of, 362. 365 

Equisetum arvense, 187-189 ; 
gametophyte of, 190 

Equisetum hyemale, 189 

Erica, 284 

Erythronium americanum (Er-y- 
thro'ni-um), 252, 253 ; forma- 
tion of flower, 349 



Etiolated plants (E-ti-o-la'ted), 65 
Euastrum (Eu-as'trum), 98 
Eupatorium purpureum (Eu-pa- 

to'ri-um pur-pu're-um), 405 
Evaporation, 35, 36 
Evening primrose, 279, 2S0 

Ferns, 165-1S6; dimorphism of, 

340-345 

Fertilization, in fucus, 115, 117; 
oedogonium, 102; peronospora, 
127 ; saprolegnia, 125 ; spiro- 
gyra, 97 ; sphaerotheca, 138 ; 
vaucheria, 108; picea, 212; an- 
giosperms, 231-234; cycas, 217 

Fibro-vascular system, 48, no 

Figwort (family), 285 

Flagellates, 119 

Florideae, 117 

Forget-me-not, 286 

Fragaria vesca, 275, 276 

Frullania, 72, 154, 155 

Fucus, 115, 116, 118 

Fumariaceae (Fu-ma-ri-a'ce-ae), 
271 

Fumitory, 271 

Fundamental system, 48 

Fungi, 56, 65 ; classification of, 
139; nutrition of, 332-337; res- 
piration in, 56; wood destroy- 
ing. 330, 337 

Gametangium (Gam-e-tan'gi- 

um), 97 
Gamete (Gam'ete), 95-97, 107, 

109 
Gametophore (Gam-e'to-phore), 

145, 147 
Gametophyte (Gam-e'to-phyte), 

143, 144/159. 164, 175, 176/190; 

of angiosperms, 228 ; signifi- 
cance of, 239-246 
Gamopetalous (Gam-o-pet'a- 

lous), 2S4 
Gamosepalous (Gam-o-sep'a- 

lous), 278, 283 
Gases, diffusion of, 49-53 
Gaylussacia resinosa (Gay-lus- 

sa'ci-a), 2S3, 2S4 
Gemmae of mucor, 22 ; of mar- 

chantia, 153 
Gentian, 287 
Gentiana crinita, 287 
Gentianaceae, 2S7, 299 



440 



INDEX. 



Geotropism (Ge-ot'ro-pism), 82, 

84 
Geraniaceae (Ger-a-ni-a'ce-ae), 

272, 295, 297 
Geum, dissemination of seed, 369 
Gingko, 216, 218 
Glacier (Greenland), 383 
Glumiflorae (Glu-mi-flo'rae), 258, 

296 
Gonidangium (Go nid-an'gi-um), 

121 
Gonidiophores, 126, 127, 
Gonidium (pi. gonidia), 75, 76, 

121, 123, 126, 127 
Gracillaria, 116, 118, 119 
Gramineae, 258, 294, 296 
Ground cherry, 285 
Growth, 75-81 
Gruinales, 272, 297 
Guttation, 40, 41 
Gymnosperms, 202-220 ; classi- 
fication of, 219 ; comparative 

table of, 220 
Gynandrous, 255 

Hamamslis, 414 

Haustoria (Haus-to'ri-a), of 

fungi, 323, 324 
Heliotropism (He-li-ot'ro-pism), 

84, 85 
Hepaticae, 140 
Heterospory (Het-er-os'po-ry), 

origin of, 351-353 
Hickory, opening buds, 415 
Hieracium venosum, 292 
Holdfasts, 93, 98, 115 
Honeysuckle, 288 
Horse-chestnut, 302, 303 
Horsetails, 187-190 
Houstonia ccerulea, 287 
Huckleberry, 283 
Hydnum, 337, 338 
Hydrotropism (Hy-drot'ro-pism), 

90 
Hypocotyl (Hy-po-cot'yl), 307, 

308 
Hyponastic (Hy-po-nas'tic, 86 
Ilyponasty (Hy-po-nas'ty), 86 

Impatiens fulva, 370 

Indian corn, osmose in cells of, 

16 
Indian-pipe, 283 ; mycorhiza of, 

320 



Indian turnip, 311, 313; forma- 
tion of flower, 349 

Indusium, 166, 170 

Inferior ovary, 255 

Insectivorous plants, 90 

Integument, 209 

Irritability, 82-92 

Isoetes (I-so'e-tes), 196-199; hab- 
itat of, 395 

Isopyrum biternatum, 270 

Jack-in-the-pulpit, 311, 313, 349, 

35p 
Jamin's chain, 48 
Jungermannia (Jung-er-man'- 

ni-a), 156, 157 

Kalmia latifolia, 362, 413 
Karyokinesis, 240-244 
Kinetic energy, 67 
Kinoplasm, 241 

Labiatae, 286, 295, 299 
Lactuca canadensis, dissemina- 
tion of seed, 370, 371 
Lactuca scariola, dissemination 

of seed, 370. 371 ; parahelio- 

tropism, 88 
Lamium amplexicaule, 286 
Leaf, epidermis of, 37; structure 

of, 36-38 
Leguminosae, 278, 298 
Lemanea, 116 

Lemna trisulca, nutrition of, 314 
Lepiota naucina, 335 
Lettuce, prickly, dissemination 

of seed, 370, 371; wild, 370, 371 
Leucoplasts, 68 
Lichens, nutrition of, 316-318; 

soil formation by, 381, 384 
Ligula, 291 

Liliaceae, 251-253, 294, 296 
Linin, 240 

Linnaea borealis, 288, 289 
Liquids, movement of in plants, 

42-48 
Liverworts, 140 ; nutrition of, 

70-72 
Lodicules, 259 
Lonicera ciliata, 288 
Lycopodium cernuum, 193 
Lycopodium clavatum, 191, 192 
Lycopodium lucidulum, 192 
Lycopodium phlegmaria, 193 



INDEX. 



44I 



Macrosporangium, 194-199 ; of 

pine 207, 209; of cycas, 214; of 

trillium, 224 
Macrospore, 194-199 ; of angio- 

sperms, 229 
Maple, 273, 274 
Marattia, fertilization, 1S2 
Marchantia, nutrition of, 70, 71; 

structure and development, 

M4-I53 
Marsh marigold, 26S, 269 
Medicago denticulata, 319 
Medulla, 44 

Micrasterias (Mi-cras-te'ri-as), 9S 
Microsomes (Micro-somes), 6 
Microsphaera (Mi-cro-sphae'ra), 

138 

Microspore, 194, 197, 199; of pine, ' 
204; of cycas, 215; of trillium, 
223 

Milkweed, dissemination of seed, 
372 

Mint family, 286 

Mitchella repens, 288 

Mnium affine (Mni'um af'fi-ne), 
72, 74, 158-161 

Monaster, 241 

Monocotyledons, 251-261, 294, 
296 

Monotropa, 2S3 

Morning glory, 2S4 

Mosses, nutrition of, 72; struc- 
ture of, 158-163 

Mougeotia (Mou-ge-o'tia), 98 

Moulds, nutrition of, 322 

Mucor, 6-8, 120-123; osmose in, 
15; mycelium, 6 

Mushrooms 136; studies of, 326- 
337; poisonous, 334, 335 

Mustard, 272 

Mutualism, 318 

Mycelium 6, 76, 121, 136; sterile 
in coal mines, 325, 326 

Mycorhiza, 320 

Myrtiflorae, 280, 298 

Nettle (dioecious), 265 
Nightshade (family), 285, 299 
Nitella, 8, 9 
Nitrogen, gathered by plants, 

3i8 
Nostoc, 118 
Nucellus, 209-211 
Nuclear plate, 241 



Nuclear spindle, 241 

Nucleolus, 4 

Nucleus 3; morphology of, 239- 

244 
Nuculiferae, 286 
Nutation, 80 
Nutrient solution, 22 
Nutrition, means for, 70-72; 

further studies in, 314 

Oak, 263 
Oat, 258 
CEdogonium (OE-do-go'ni-um), 

99-103 
GEnothera biennis, 279, 280 
Onoclea sensibilis (On-o-cle'a 

sen-sib'i-lis), rhizome, 168; 

dimorphism of, 340-345 
Onograceae, 2S0, 298 
Oogonium (O-o-go'ni-um), 99, 

100, 102, 107, 108, 112, 123, 124, 

127 
Oospore, 100, 108, 128 
Orchidaceae, 255, 256, 296 
Orchids, pollenation of, 360-363 
Oscillatoria (Os-cil-la-to'ri-a), 118 
Osmose, 13, 18 
Ostrich fern, 345, 346 
Ovule of pine, 207; of trillium, 

224 
Oxygen, 51, 52, 54 

Palisade cells, 37 

Palms, 257; cocoanut palms, 257 

Papaveraceae, 271 

Papilionaceae, 278, 295, 298 

Pappus, 291 

Paraheliotropic, 88 

Paraheliotropism(Par-a-he-li-ot'- 

ro-pism), 90 
Parasitic fungi, nutrition of, 322, 

323 
Parenchyma, 44, 48 
Parmelia, fruit of, 318 
Parsley, 281 
Parthenogenesis, 127 
Partridge berry, 288 
Passifiorinae, 298 
Pea (family), 278 
Pear, 277 

Peltigera, 316, 317 
Pepper, 235 
Pepper root, 225 
Perigynium, 260 



442 



INDEX, 



Perigynous, 275 
Perisperm 234 
Perithecium, 136-138 
Peronospora alsinearum (Per-o- 

nos'po-ra al-sin-e-a'rum), 125, 

127, 128 
Peronospora calotheca, hausto- 

ria of, 324 
Personatae, 285, 299 
Petaloideae (Pet-al-oi'de-ae), 251, 

296 
Phaeophyceae (Phae-o-phy'ce-ae), 

115, 118 
Phloem (Phlo'em), 45, 47, 48 
Photosyntax, 61 
Photosynthesis, 61 
Phycomycetes (Phy-co-my-ce'- 

tes), 128 
Phyllotaxy, 306 
Phytophthota infestans (Phy- 

toph'tho-ra in-fes'tans), 126, 

127, 128 
Picea vulgaris, 212; fertilizatibn 

in, 212 
Pine, new growth, 416 
Pine, white, 202-213 
Pines, reforestation by, 378, 379 
Pinus strobus, 202-220 
Piper nigrum endosperm and 

perisperm of, 235 
Plant body, 72, 73; members of, 

73, 74; leaf series, 74; stem 

series, 73; root, 74 
Plant communities, 410 
Plasmolysis (Plas-mol'y-sis), 19 
Plasmopora viticola (Plas-mop'o- 

ra vi-ti'co-la), 125, 126, 128 
Platycerium alcicorne, 345 
Pleurococcus (Pleu-ro-coc'cus), 

118, 119 
Plum (family), 276 
Plumule, 308 
Podophyllum peltatum, 229-231 ; 

karyokinesis in, 240-243 
Pollen, of pine, 204 ; of cycas, 

215 ; of trillium, 223 
Pollenation, 351-367; of pine, 206, 

208 
Polycarpicae (Pol-y-car'pi-cae) 268, 

297 
Polygonacese (Po-lyg-o-na'ce-ae), 

267, 297 
Polygoniflorae, 267, 297 
Polygonum sagittatum, 267 



Polymorphic, 135 
Polypetalous, 278 
Polypodium vulgare, 170, 239 
Polyporus (Pol-yp'o-rus), 338 
Pomaceae, 276, 295, 298 
Pontederia, 406 
Poppy (family), 271 
Porella, 155 
Portulacaceae, 268, 297 
Potential energy, 67 
Powdery mildews, 136 
Primrose, 355, 356 
Primula, 284; pollenation of, 356 
Primulaceae, 284, 299 
Primulinae, 284, 299 
Procambium strands, 47 
Progeotropism (Pro-ge-ot ro- 

pism), 82, 83 
Promycelium (Pro-my-ce li-um), 

134-136 
Proterandrous, 360 
Proterandry, 362 
Proterogynous, 360 
Prothallium, of ferns, 176-1S2; 

of pine, 209, 210; of cycas, 214, 

215; of angiosperms, 228-233 
Protococcoideae (Pro-to-coc-coi'- 

de-ae), 118, 119 
Protococcus (Pro-to-coc'cus), 118, 

119 
Protonema (Pro-to-ne'ma), 163, 

178, 180 
Protoplasm, 1-12; movement of, 

7-1 1 

Prunus virginiana, 277 
Pteridophyta (Pter-i-doph'y-ta), 

200, 201 
Pteris aquilina, 178 
Pteris cretica, 245 
Pteris serrulata, spores of, 177 ; 

embryo of, 183, 186 
Puccinia graminis, 129-136 
Pumpkin, roots of, 77, 78 
Pumpkin seed, germination of, 

309-311 
Purslane, 268 
Pyrenoid, 2 
Pyrolaceae, 283, 299 
Pyrola elliptica, 283 

Quercus rubra, 263 
Quillworts, 196-198 

Ranunculaceae, 268, 294, 297 



INDEX. 



443 



Rattlesnake-weed, 292 

Red algae, 116, 119 

Red rust, 129 

Red-snow plant. 118, 119 

Reforestation of lands, 376, 379 

Respiration, 54-5S ; intramolecu- 
lar, 58 

Rhabdonia (Rhab-do'ni-a), 117, 
119 

Rhizoids (Rhi'zoids), 71, 72 

Rhizome, of trillium. 221 

Rhizomorphic (Rhi-zo-mor'phic), 

325 
Rhizopus nigricans (Rhi'zo-pus 

ni'gri cans), 120-123 
Rhododendron nudicaulis, 411 
Rhodophyceae (Rho-do-phy'ce- 

ae), 116, 119, 139 
Rhceadineae, 271, 297 
Rock lichens, 382-384 
Root hairs, 24; absorption by, 19, 

25, 26; acidity of, 27; corrosive 

action of, 27 
Root pressure. 31, 32, 39, 40 ; 

periodicity of, 32; variation of, 

32 
Root tubercles, 318 
Rosa, 276 

Rosaceae, 275, 295, 298 
Rose (family), 275 
Rosiflorae, 275, 298 
Rubiales, 288 
Rubus odoratus, 275, 276 
Russian thistle, 268 
Rusts, 129 

Sac fungi, 136-138 
Sagittaria, 255 

Sagittaria heterophylla, 402-404 
Sagittaria variabilis, 400, 404 
Salicaceae, 262, 294, 296 
Salsola soda, 268 
Sand dunes, vegetation of, 376 
Sanguinaria canadensis, 271 
Saprolegnia, 123-126 
Saxifraga virginiensis, 274 
Saxifragaceae, 274, 298 
Saxifraginae, 274, 298 
Scorophulariaceae, 285. 299 
Seeds, distribution of, 368, 373 
Selaginella, 193-195, 199-201 
Sensitive fern, dimorphism of, 

340-346 
Sensitive plants, 89, 90 



Silkweed, dissemination of seeds, 

372^ 
Silphium laciniatum, 88 
Siphoneae (Si-pho'ne-ae), 109, 118 
Skunk's cabbage, 356, 357 
Soil formation, 381-3S8 
Solanaceae, 285, 299 
Sorus, of ferns. 166, 170, 173 
Spadiciflorae, 257, 296 
Spadix, 257 
Spartium, scattering of pollen, 

364 

Spathe, 257 

Spathyema fcetida, 257 

Spectrum, bands in, 67 ; absorp- 
tion bands of, 67 

Spermagonia, 132 

Spermatia, 132 

Spermatozoids in gymnosperms, 
216-219 

Sperm cells, 146 

Sphaerella nivalis (Sphae-reTla 
ni-va'lis), 118 

Sphaerotheca (Spbae-ro-the'ca), 
138 

Sphagnum in moors, 386-394 ; 
structure of leaves, 394 

Spiderwort, II 

Spirodela polyrrhiza, 315 

Spirogyra, 2, 93-98 

Sporangium, of ferns, 167-175 

Spores, of riccia, 143 ; of ferns, 
169-172 ; of equisetum, 188 

Sporidium, 134, 136 

Sporocarp, 112, 113 

Sporogonium (Spor-o-go'ni-um) 
of riccia, 142 ; of marchantia, 
T49, 150; of foliose liverworts, 
155—157 5 of mosses, 161, 162 

Sporophyte (Spor'o-phyte), 143, 
144, 150, 152, 156, 157, 159, 164, 
175, 182, 199 ; of angiosperms, 
228 ; significance of, 239-246 

Squirrel corn, 271 

Staghorn fern, 345 

Starch, 59; test for, 59, 60; trans- 
location of, 61; where found, 
60, 61, 63 

Starch grains, form of, 63 

Staurastrum (Stau-ras'trum), 98 

Sterigma, 134 

Stoma (pi. Stom'a-ta), 38 ; action 
of, 39 ; demonstration of, 41 

Strobilus, 192 



444 



INDEX. 



Sundew, go 

Symbiosis, 318 

Sympetalae, 283, 298 

Synergids (Syn-er'gids), 231, 233 

Taxodium distichum, 395 
Teasel, 289 

Teleutospore, 130, 135 
Temperature, 91, 92 
Tensions, tissue, 29, 30 
Tetraspores, 117 
Tissues, synopsis of, 48 
Touch-me-not, dissemination of 

seed, 370 
Transpiration, 33-41 
Trichomes, 48 
Trillium erectum, 251 
Trillium grandiflorum, 221-224 J 

formation of flower, 347, 348 
Tubiflorae, 284, 299 
Turgescence, 14, 28 
Turgescent, 15 
Turgid, 15 

Turgidity, 28 ; restoration of, 28 
Twin flower, 289 

Ulmaceae, 266, 294, 297 
Umbelliflorae, 281, 298 
Uncinula, 136, 138 
Unifolium, 254 
Uredineae(U-re-din'e-ae), 129-136, 

139 
Uredospore, 131, 135 
Uromyces caryophyllinus, 323 
Urtica, 265 
Urticaceae, 265, 297 
Urticiflorae, 265, 297 

Vascular bundle, 43 ; structure 

of, 44-47 
Vaucheria, 105-109 
Vaucheria geminata, 108 



Vaucheria sessilis, 106-107 

Vessels, 45, 46 

Vetch, root tubercles of, 318, 319 

Vicia sativa, dissemination of 
seed, 369 

Viola cucullata, 354 

Violet, endosperm and embryo, 
235 ; pollenation of, 353, 354 

Virgin's bower, 269, 270 ; dis- 
semination of seed, 372, 373 

Volva, 334, 335 

Wake robin, 221 

Walking fern, 173, 413 

Water moulds, 123-126 

Water plantain, 254 

Water vapor, 34 

Wheat rust, 129 

Whortleberry, 283 

Wild carrot, 281, 282 

Willow, 262 

Witch hazel, 414 

Wolffia, 315 

Wood fibres, 48; parenchyma, 48 

Xanthidium, 98 
Xylem, 44, 45, 47, 48 

Yellow water lily, 407 

Zamia, 219 

Zamia integrifolia, 216 

Zonal distribution of plants, 

400-408 
Zoogonidium (Zo-o-go-nid'i-um), 

toi, 102, 105, 106 
Zoospores, 101, 103, in, 112 
Zygnema (Zyg-ne'ma), 98 
Zygomorphic, 289 
Zygospore (Zy'go-spore), 2, 95. 

97, 98, 122 
Zygote (Zy'gote), 95, 122 



July, 1898. 



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